Android apps can be distributed in the .APK format outside the Android Market. Use these steps to install an .APK file to your Verizon Samsung Fascinate smartphone.
1. Open Settings.
2. Tap Applications.
3. Check Unknown sources.
4. Download and install Astro File Manager from the Android Market.
5. Connect the Fascinate to your computer with the included USB cable.
6. Slide down the notification panel at the top of the screen and tap USB connected.
7. Select Mount.
8. A removable disk should now be available from your computer. Drag and drop the APK file to the removable disk.
9. Open Astro File Manager.
10. Navigate to the APK file location on the SD Card. Tap it and select Open App Manager.
11. Tap Install.
12. Tap Install again.
The app should then be installed on the Samsung Fascinate.
Another app you can use to install APK files is ApkInstaller.