Speaker system wiring advice...please help

I just purchased a kicker kmt6's and am looking to install them onto my tower sometime this week and would like some quick advice as to the best way to do it. Currently there are 4 speakers on the boat with only the headunit powering each speaker. I have a two channel amp that I would like to use to power the tower speakers. I am handy but not very knowledgable with speaker wiring. What do I need to do to still retain all four speakers on the boat yet still be able to power the tower speakers. Thank you very much!!!

it really depends on how far you want to go with your system and good you want it to sound..