Several ways to do it.
Do you want to set up a "stereo" feed or two separate feeds?
Stereo is pretty easy, Run the audio from each scanner into a stereo AUX input, change the feed software to stereo, and up the bit rate to double the mono rate (All after getting the ok from RR)
Two separate feeds usually requires a bit more and doing a search on this topic for "multiple feeds" will get you several posts on how others are doing it.
Bruce