Hello willieaames and welcome to these forums. You'll find many helpful people here and a lot of useful information. Make sure that you:
Assuming that the levels are OK, you select that audio input from the list for the track (right-click the RecArm to see the Input list). Details can be found in the User Guide.
Also, can you post a pic of the audio inputs available in Reaper's Preferences / Audio / Device?
How to describe your hardware set-up (in Post #3)
How to post screenshots (in Post #2)