Ok so the basic ways to add allies in the game are
1: This will allow you to add random people of around your level. Click the Allies button, click search for allies, then press recruit on the various people.
2: This way will allow you to add people based on their game ID. Click the Trade button, click inside the 'Enter user ID' text box. Then enter the desired users ID, hit done, then hit Search ID. This will bring up their profile, which will allow you to either recruit and/or trade with them.
Hope this helps