here is how the side marker installs...
the far left side you can see where it slides into a slot in the fender, the right side has the little plastic hold in clip.. you go from inside the fender, and you can squeeze that clip inwards with just your fingers, and it will pop right out.
then you remove the bulb socket by twisting counter clockwise, and then the "194" bulb can be pulled straight out from the socket.. it might take a bit of force, those 194's can be a PITA sometimes.