If you are a new Mac user, switching from Windows, or just new to computers in general, you may not know there is something a little bit different in the way you install programs on Mac OS X.
Many people I know run into trouble installing applications they download from the internet, simply because they are not used to dropping an application into the “Applications” folder from a mounted virtual disk. My brother had 4 copies of Google Earth downloaded, none installed, and wondered why it was “reset” every time he tried to run it. So, for those of you out there trying to figure out why you cannot just drag the icon into the dock and run it at will, here is a tutorial made just for you.

First, download your application. In OS X, on Safari, the default location for your downloads is in your “Downloads” folder, located inside your “Home” folder. To access this location, find “Finder” on the left hand side of your dock (by default.) It looks like this:

Finder

When you click on the icon in the dock it will open a new Finder window.  You can accomplish this same task by holding down ⌘ and hitting N, or “Command-N”. Be sure it says “Finder” by the  in the menu bar, upper left hand corner of your screen.  You should see something similar to this:

New Finder Window

I am currently running OS 10.6.1, Snow Leopard, but the above ⌘-N works throughout OS X.  Also, I have already clicked on the “Home” folder (looks like a house) and the Downloads folder inside of Home.  That is why they are highlighted in blue.  If you do not have this view enabled, it may look like this:

Cover Flow View in Finder

You can see the top center of the window shows my Home Folder, meaning this is the directory you are currently located in.  You can use your arrow keys to navigate down the list shown in the bottom half of the window until you get to the “Downloads” folder.  Hitting enter, however, will not get you into that folder.  You can use ⌘-Down Arrow to go into the folder, or you can use ⌘-Right Arrow to open the folder’s contents and display it in the list.  As a matter of fact, when you select any file and want to open it, using ⌘-Dn (I’ll list command-down arrow like ⌘-Dn from now on) will work.  You can also hit spacebar to see a QuickView of the file.  Yet, I digress.

So, now that you are in your “Downloads” folder, you can find the file you have recently downloaded.  I will use Google Earth as my example here:

Google Earth Download Page

When you click the “Agree and Download” button, you see a new “Downloads” window open, and the file begin to transfer to your computer:

File Transfer In Progress

After the file transfer completes, a bunch of stuff happens.  First, OS X verifies the disk image is not corrupted, and then it will mount.  A file with “dmg” after the period means “Disk Image”, which basically means it is just like a CD or DVD you would put into your drive.  If you had a physical disk and stuck it in your DVD drive, it would show up on your desktop, and you could click on it.  Same goes for .dmg files, but you don’t need the physical disk:

Google Earth Downloaded and "Mounted"

The download automatically verifies, and “mounts” on your desktop, just like you had a Google Earth CD and put it in your drive.  The white thing above the disk name on my desktop there is the icon for a virtual disk, or some USB drives as well.

You can also see the actual Google Earth application in the window titled Google Earth and the virtual disk picture just to the left of it.  If you close that window, the disk stays mounted on your desktop.  What you want to do now is actually install the program by dragging it to somewhere on your computer.  This is done simply by holding down the left mouse button (trackpad button, or sometimes your only mouse button) and moving it off of the window it is currently in.

I recommend always installing programs into your “Applications” folder, to keep everything nice and tidy.  Open a new “Finder” window, and below your home folder it says “Applications”. Click on the link, and it will open your “Applications” folder to the right hand side:

Installing into Applications Folder

One thing to note here is above the “Applications” link, there is the Google Earth disk image with an Eject symbol next to it.  More on that in a second, first let’s install Google Earth. Get your two windows side-by-side on your desktop, and drag the Google Earth application from it’s current window and drop it on the list in the “Applications” window.  Before you let go of the mouse button, be sure there is a little green “+” sign, letting you know the file you are moving is going to be copied into this location.  If you see it, go ahead and drop it in there:

Side-by-Side

Look for the + Sign

Now that you have installed and application, you can unmount the disk image.  First, close the window titled “GoogleEarth-Mac”.  Next you can either click the eject button next to the GoogleEarth disk in the “Applications” window you still have open, or you can click once on the disk image on your desktop to highlight it.  You can then drag it to the trash can in the dock (with turns into a big Eject button), or you can use the keyboard shortcut ⌘-E (command-e for  ”e”-ject.)

Lastly, if you want to back up your GoogleEarthMac.dmg file, you can do so.  You can leave it in your “Downloads” folder, or you can delete it.  To delete it, navigate back to your “Downloads” folder, in your home directory, and highlight the .dmg file:

Highlight the File in Finder

To send it to the Trash, simply drag it there and let go, or hit ⌘-Delete.

That’s all there is to installing an application on OS X.  Once you can effortlessly find your way around the windows, installing is as easy as drag and drop!