You should consider using CocoaPods to manage your projects' dependencies. It works just like Ruby gems, and you only have to do this:
Add a file named Podfile
platform :ios
'Mantle', '0.2'
Then install dependencies
$ gem install cocoapods
$ pod install
After this last command, don't use your .xcodeproj
anymore. Use the .xcworkspace
.
To look for other frameworks
$ pod search restkit // For instance