The white clips need to be removed from the door and installed onto the door panel for re-assembly. There is a special tool to remove the clips while the door panel is still on the vehicle. It doesn't sound like you have the tool (no pun intended with reference to your name - lol). If the clips break upon removal, you can get them at any local body shop or at some auto supply stores. Depending on the amount of damage to the back side of the door panel when it was removed, there may be a way to reattach the clips to the panel (again, maybe a local body shop can help. The plastic cover (actually a moisture barrier) needs to be reinstalled. If its still in one piece, you can reuse it. Make sure it is sealed to the door just as it was when you removed it. If it has a small tear, you can duct tape it. Good luck.
