Xcode Project merge.

Hi all, i'm new about xCode - Objective-C language programming,

I have only one question.

How can i merge two different projects in only one?

I've made an application that requires a photogallery, but i wanted the same photogallery like iOs do in "Photo", so I looked for it on the net and i've downloaded one that makes what i want, but now i don't know how to implement the gallery in my own app,

Somebody can help me?

thank you anyway!