Then to the hardware store. Since I haven't yet drilled any holes for the towel bar, I had more freedom to pick hardware. I picked some self-tapping drywall anchors that look like big white plastic cartoon exaggerations of screws, which you SKA-ROOO into the drywall and then screw actual screws into them.
Also, a guy finally came today to fix that spot in the shower with missing tile. On Friday I'll be able to use the shower. So, once I get the towel bar put up (maybe tonight!), the hardware work on the bathroom will be complete! Then we'll just need to put in some furniture to put towels and things in.