So easy. Turn the rod with one hand on either side of the middle until it almost fits, place it in the area you want it to be, then continue to turn the rod until it's tight. To remove, just turn the rod in the opposite direction until it loses its grip. There are instructions included in the package for further advice.
You can't adjust the tension. It does not create any tension. You have to get a different model shower rod.
1 1/4 inches
may be 1.5"