Use a flat blade driver to prise of the inner door handle cover, remove both screws inside.
Remove one screw on the front-bottom corner of the speaker pod, and 2 others along the bottom of the door trim skirting.
Use a very, very fine flat blade to prise out the little red tabs in the door locks; you will quite possibly crack the tabs or the plastic surround, someone may have an idea how to do it an easier way. Remove the tab, pull the grey plastic surround out and remove that screw as well.
Remove the two or 3 visible screws in the door A/C vents, you may also have to pull out the top vent to get to a screw holding the whole section to the door. Take care of the other 3 first, and if the section still won't budge, investigate further.
Once all these screws are out, you should be able to pull the door trim straight off.
Oh and also, 6.5" speakers will not fit very well without cutting the plastic sheeting that is underneath the door trim, and depending on the size of the magnet, they may not fit inside the door frame; the magnet could rest against a metal piece behind the speaker hole/ If this is the case, do everything you can to mount it extended from the door frame, but
make sure you put something between the magnet and the metalwork to stop it from vibrating, it will drive you insane otherwise. Personally I would suggest you find some 6" speakers instead, but if your mind is made up, your mind is made up
Research your wires and polaritys before you connect anything. Check the wiring diagrams for your speakers, check the wiring diagrams for you cars, and make sure you get them right. Solder/connect the terminals, whichever you need to do, and make sure the terminals don't touch the door frame. Ordinarily this would not be a problem, but if you get stuck mounting the speakers not flush with the hole, the terminals may line up perfectly to touch the door frame. Use heatshrink to cover the terminals, and of course, do the same to any soldering joints anywhere. Make sure you leave no exposed wires anywhere they can touch anything else.
I hope your speakers are not splits; they may sound way better, but you will struggle like a mofo trying to run tweeter wires through the rubber door grommet if they're inline crossovers.