Coecting Line-Level Sources to the TRS Jacks, CS18AI

Could you please help me?

I have started using CS18AI since few days. Before I had been using Surface to handle RM32AI.

I need to use Line-Level Sources to the TRS Jacks, but I caot understand how the source could arrive to a chael of RM32.

I have the same problem with the line MIC Talkback.

Thanks for your help! Waiting for your answer.