You could use cocoapods to manage your dependencies, it's simple to use and to update.
IMHO, it also makes your project cleaner.
If you still want to install it manually, make sure you have followed this "tutorial":
https://github.com/BradLarson/GPUImage#adding-the-framework-to-your-ios-project
Otherwise, use cocoaPods! :
1- open terminal
and install cocoapods with gem
:
$> sudo gem install cocoapods
2- go into your project folder:
$> pod init
// it will create a Podfile
3- Edit the Podfile and copy past:
platform :ios, "7.0"
pod 'GPUImage', '~> 0.1.0'
// save and close the file
4- install dependencies:
$> pod install
// on a successful install enter:
$> open projectName.xcworkspace/
// it will open your xcode project with your dependencies already set up
5- Import GPUImage in ViewController
6- Enjoy!