Keys are part of your profile. You can't just add keys. You can reassign a save file with keys.... But if you have gibbed why would you want to do that when you can make anything you want?
If you can't figure out how to make a gun you need to watch a tutorial online. It's pretty simple and there is a link on gibbed to the gear calculator that shows you want you will get using what parts. --- PSN: SICARII (The i's are lower case L's.)