I have the Nikon D7100. I shoot it on AF Single 90% of the time. But I don't know how to select a focus point inside the viewfinder. When I push the shutter release halfway down, all I see is one focus point, not several. It glows red for about a second or two, then it goes black. How do I select a focus point?
For moving the focus point(s) around you need to have a look at the « wheel » button which you also use for browsing on camera through the pictures taken
1/ ensure that the switch (which is on the outer part) is NOT on L (if it is on L, the selected focus point is Locked and you can’t move it)
2/ once you have halfway pressed the shutterrelease, use the wheel style button to move it up/down or left/right.
The camera will « remember » which focus point you selected, until you change it.
The same is possible if you select groups of focus points