Boss rc505 looper as audio interface

HI
I use the rc505 as my sound card interface. It works great for in conjunction with GP as I can load up loads of sounds and samples and layer them. The problem is when I want to use my voice or guitar through the RC505, I get loop feedback. Anyone now how I can bypass or fix this.

Regards

Marty

Does it have a button for direct monitoring and or software options regarding the monitoring?