1. Adding the dependency

Just like any other API. Add it as a reference in your C# client project. Check the FiveM docs for info on how to setup a C# resource.

2. Using the API

Checkout the example menu provided in the download. It’ll show you exactly what all the features are. The rest is up to you.

3. Where can I find a reference of all functions/classes/types/whatevers?

Coming soon on these docs. Currently, use the source code as a guide (there’s comments in there for a reason). And use the example menu for some basic info. It’s designed similar to NativeUI’s structure, so if you’re familiar with NativeUI (C# version) then this shouldn’t be hard to switch to at all.