I have a 07 F150 with a D3 in it and would like to add a 12 sub and an amplifier. It has been a while since i Have done this. What is the best and easiest way to do this?

Buy an amp, a sub, and an amplifier wiring kit. Then hook it all up. The D3 has a subwoofer pre-out.

Yep, theres a blue wire for remote turn on of the amp, and then rca outs for the sub. Be sure to run the power and rca/remote lines on opposite sides of the truck to avoid static in the rca lines.