Tmitchell- First, I don't know anything about the Proceed. But assuming that it is a three channel amp, short the inputs of the unused channels, and to alleviate any concerns, place a 4 to 10 ohm power resistor on the output posts of the unused channels for dummy loads. The resistors may or may not be necessary depending on the amp topology. However, they are cheap insurance, or at least, piece of mind.
If you have any those cheap interconnects that come with equipment, just cut the cables about two inches behind the connector and strip back the insulation from the inner conductors. Then just twist or better yet solder the inner conductor to the out shield wires, and tape or shrink tube the exposed end. You have a cheap shorting plug that should do the trick. Good luck.
