I wouldn't recommend it, as the microphone input is a low level signal, whereas the output of your Behringer is a much higher level signal. You would have to attenuate the signal from the Behringer before connecting it to the microphone input.
how are you hooked up? (hopefully you have this problem fixed by now. looks like you have 2 options for inputs. You can use xlr or 1/4" Are you hooking up to a sub as well or just flying these solo? Make sure your mixing board master is up, channel on mixing board is up, plug volume on speaker is up.. Im curious if you did get these fixed. Personally, I use qsc..
1... download manual ! Find it on the web.
2... get the right connector or have it made. Guitars are low-signal instruments, you will need a Plug to XLR adapter to get to the Mic input.
Peace...