How to enable the checkbox for unknow source on your Android phone

Enable "unknown source" (for Andriod users only) 
- Settings ->Applications -> Device Administration-> Choose "unknown source" 

Android 2.1 (Motorola DROID / Milestone)
-Settings->Applications-> Unknown sources
• Open the app drawer
• Open the Settings app
• Tap on "Applications"
• Enable the checkbox for "Unknown sources"
• Confirm the warning with "OK"

Android 2.2 (HTC Desire)
• Open the app drawer
• Open the Settings app
• Tap on "Applications"
• Enable the checkbox for "Unknown sources"
• Confirm the warning with "OK"

Android 2.3 (Samsung Galaxy Tab)
• Open the app drawer (tap on "Applications" in the dock)
• Open the Settings app
• Tap on "Applications"
• Enable the checkbox for "Unknown sources"
• Confirm the warning with "Yes"

Android 3.2 (Samsung Galaxy Tab 10.1)
• Tap on the clock in the lower right corner
• Tap on "Settings"
• Tap on "Applications"
• Enable the checkbox for "Unknown sources"
• Confirm the warning with "OK"

Android 4.0 (Samsung Galaxy Nexus)
• Open the app drawer
• Open the Settings app
• Tap on "Security"
• Enable the checkbox for "Unknown sources"
• Confirm the warning with "OK" 

Kindle Fire
• Tap the gear icon in the top status bar
• Tap on "More…"
• Tap on "Device"
• Set "Allow Installation of Applications" to "ON"
• Confirm the warning with "OK"