If you want to run the same area many times back to back, you will need to create new instances. You can do this by Ctrl+Clicking the waypoint marker on the World Screen of the area you want to rerun while you’re at a waypoint, or the entrance to the area you want to rerun when you’re in an adjacent area. This opens the Instance Manager, which displays all of the instances of that area that you currently have access to, how long they have until they close, which servers they are connected to, and which players are in each one.