Need help installing one mono amplifier to a four channel amplifier.

Currently, I have a pretty decent sound system in my car but I would like to add a mono amplifier to my 10'' JL subwoofer. I have the current subwoofer and my four speakers bridged to my infinity amplifier under the passenger seat. I would love for anyone to lend me a hand here to how to install that mono amplifer to my subwoofer and know all the wiring and what not.

Thanks.