cubase 6.5.5 with behringer xair xr18

Hello community.

I have been using Cubase 6.5 for the last couple of years and I absolutely love it I also have been using it with the Tascam us 1800 interface. We recently purchased the Behringer xr18 and I am trying to get that set up to using Cubase. I have spoken with a couple users that also on the Behringer xr18 and they tell me that they use Channel 17 and 18 as the main outputs which allows 16 channels of simultaneous recording along with a 6 auxiliary sends as six independent headphone mixes. My problem is I am having an issue connecting the xr18 2 Cubase. I can get the inputs to work and registering Cubase when tracking my issue is when playing back I have my monitors hook straight up to 17 and 18 I have those said his outputs in Cubase but I still don’t hear any audio. I guess what I’m looking for if someone to help me walk through setting it up to where I have 16 channels of recording, channels 17 and 18 as the main outputs.

Make sure that usb is selected on Chanel’s 17/18. That setting is on the channel page near the top

Make sure that usb is selected on Chanel’s 17/18. That setting is on the channel page near the top