Once you have asuccessfully built your app, you have an .apk file. The .apk file is the compiled, digitally signed version of your code, packaged ready for distribution.

To install it on a device, you need to enable installation of non-Market applications first:

Go to your device’s Settings page
Tap Applications
Ensure Unknown sources is checked
You then make the .apk file available on your device:

Dropbox (or similar)
If you use Dropbox, or a similar file synchronization service, drop the .apk file into your shared folder. Navigate to it on your device, and open it. You are prompted to install your app.

USB storage
Connect your Android device using its USB cable, and enable USB Storage. Copy the .apk file to your device. Use a file manager to open the file; you are prompted to install your app.

Android SDK
If you have the Android SDK installed on your computer and are familiar with its use, you can use the adb install command to install your app.