In my opinion, being a beginner (as I am too) this type of multiphysics problem where all modes of heat transfer and reaction kinetics should not be solved at first.
Start with a LTE model (simultaneously seeing the fluent theory, user guide and UDF manual). Try to implement small UDFs, like material properties, BCs, source terms etc.
Then switch to LTNE model. This will help to implement UDS for solid temperature calculation.
Then combine LTE+P1 radiation (or any other) model. Implement UDS/UDF as desired.
Till this point, it would be clear to you how fluent behaves and handles the equations. Now you can simulate LTNE with source terms.
Although, LTNE model is not explained in detail anywhere. One can gain experience by practice only.