I changed the passenger's side door handle on my jeep and now it won't open.
If the door is not opening, then either the linkage has become disconnected or there is an issue with the door latch itself. The door panel will need to be removed so the linkage can be inspected. The latch may also need to be lubricated if it is mechanically jammed. You may want to enlist the help of a mechanic, such as one from YourMechanic, who will be able to inspect, diagnose, and repair the passenger door latching system.