well if its bridged now, your on verge of smoking that sub. the amp will do about 600 bridged. your sub is 150rms so give ir take a max of 300-400.
to run single channel just connect sub positive to amp positive, then sub - to amp -. on channel one or two your choice. set gain accordingly, don't max out the gain, you'll overdrive the amp, and cause it to get hot and go into protect mode until it cools down again. its not really a risk of damaging anything just annoying to have the amp shut off repeatedly.
to adjust gain, start @ about 1/4 gain and turn up until it starts to distort and seems like it really isn't getting any louder. do this with radio turned up to the level you feel is as loud as you will be turning it. for example, i turn my radio up about 3/4 and don't go past that, so i set my gain w.radio turned up 3/4 way.
also what type of box r u running? sealed, ported. bandpass?