Kicker uses a 4” (I think) round hole. It’s not made to replace an existing rectangular unit. Didn’t it have instructions? What help are you looking for. Black ground, red power, yellow trickle, blue amp, and 4- two wires of same colors for speakers.
The cutout in the helm for our factory stereo was something like 3.5" H x 8.5" W. I just looked up the specs for the Kicker and the cutout circle is 3 5/8". Make a plate like ours and slightly enlarge the factory opening where needed. Use starboard or some kind of acrylic to cover the opening.