Easiest way for the assignment of buttons, switches, rotary encoders etc. is using LINDA which stands for Lua Integrated Non-complex Device Assigning.
The people of flighsimeindhoven.com made a great tutorial on setting up the Computer with LINDA and assigning the functions to the devices.
- LINDA Lesson 1 Install and Basic setup
- LINDA Lesson 2 Create Aircraft Module
- LINDA Lesson 3 Creating Macro’s
- LINDA Lesson 4 Consolidating macros
It starts from very basic steps 1 and 2 and goes up to experienced macro stuff for advanced users.
Bear in mind, that you need to have a purchased copy of FSUIPC for running LINDA.