I have a 3210 connected to a AP12. This might help after you read the manual as E sugested. The main input conection which has a bunch of wires and several are associated which nema out. run these to a terminal strip or crimp then connect to nema input wires on the auto pilot. I like using a terminal strip becuase you can connect other stuff to the chartplotter nema out such as VHF and merc smart craft. Mine is all 183 and I guess?? yours will be too. You may have to visit the 4212 menu to select the type of output. But you will need both manuals, it is real easy. Again all I said was for an older model and is probably somewhat different than yours. If yours has the garmin network hub for sounder and radar, you probably won't have to fool with that, just the little bitty wires in the main harness that also contain the power input.
__________________
Knotreel aka Hammer | 
simrad ap16 and garmin 4212 
