To use Theia, simply add the following line to your program:
We attempt to provide sufficient documentation but often further documentation can be found in the source code itself. You will likely find the Tutorials useful as well. Additionally, (nearly) every file is covered by a unit test that can be viewed as an example use case of the various methods and classes in Theia. If you have looked at the documentation, the tutorials, the source code, and the unit tests and still have confusion please email the Theia mailing list
Finally, it should be noted that all the code in Theia is under the namespace theia, so you will have to reference that namespace in order to use functions from this library.