Just reread your post. That will teach me to skim through it. Temporal beef is correct. You use the slider to set the focal point. If you want to be able to tap then use the focus lock.
If your in pro mode and tap the AF button this will give you a manual slider to set the focus point. Just move it until which area you want as the focal point is in focus. Or if you want the tap method. Long hold the screen and use the focus lock to tap the area and this will then stay as the focus point.