Steps
Go to http://www.developers.facebook.com
Login
In top right corner, click on Register Now button
Complete all 4 steps
After it click on Apps
Now click on + Create New App button
Type any Name which you want and press Continue button
Complete Captcha
Here disable Sandbox Mode
Click on Website With Facebook Login and in site URL: type http://www.facebook.com/mobile
Click on Save Changes button
Now you have done it, Note App ID. You can use this ID in #2 FBAD
Same as this you can create many applications
You can also change icon of application by clicking on icon of application.
Here you have need to just change only Primary Icons. No need to change other icons.