TTStyle was formerly part of the now deprecated Three20 library, and has been extracted as a standalone package for apps depending on the library to be able to piecewise migrate from it.
https://github.com/facebook/three20
Commit history from Three20 has been removed to minimize size, but a version with that included can be introduced if it is important to others.
Collapsed TTCore and TTNetworking libraries and copied key classes into the single library.
TTStyledText.h is currently not included in the project, because of its dependency on TTNetworking.
Add Header Search path, for example $(PROJECT_DIR)/../path/to
Add Three20Style as a project dependency of your application and add libThree20Style.a to the Link Binaries phase
Also note that one should remove the library prefix when importing headers, like this:
#import "Three20Style.h"