Installing an .apk file in android emulator

1. Launch your emulator
2. get an .apk file that you want to install in your emulator
3. navigate to your android-sdk dir and search for adb.exe
4. copy the location of the   adb.exe
5. Right click on my computer and open Advanced Settings and click Environment Variable
6. select Path from System Variables and click on Edit
7. add a semi-colon ';' and Paste the location that we copied
8. open cmd.exe
9. change the directory to where you have the .apk file located.
10. after you have reached the directory type :

            adb install filename.apk

and you are done .

Extracting .apk files from your Android

Using a file manager like "EStrongs File Manager" or "ASTRO File Manger" (downloadable from the Market)

• Prerequisite: Rooted device

Using ES File Manager

• Open ES File Manager
• Click on the menu button of your device
• Click on "Manager"
• Click on "App Manager"
• Long press on app you want to extract
• Click on "backup"
• Extracted .apk files will be placed on the "backups" directory of your sd card

Using ASTRO

• Open ASTRO File Manager
• Click on the menu button of your device
• Click on "tools"
• Click on "Application Manager/Backup"
• Choose apps to backup and click on "backup" to finish
• Extracted .apk files will be placed on the "backups" directory of your sd card

ENJOY!!!

ASTRO File Manger Download link       

ASTRO file manager