The final piece of the puzzle is in place. I scoured the internet for a harness and decided to get one from Upper Limits and I'm glad that I did. The harnesses have instructions but there's nothing like a human telling you that you need to double back on your buckles or that you can belay and climb on the auto-belay through the belay loop but for climbing you need to have two points of contact for your rope.
I also got to try on the harness and climb in it before I made my decision.
Behold, my Black Diamond Momentum Al harness (XL size):
At first, it felt weird not climbing in the rental Yates -- probably because I've been renting and wearing the Yates exclusively. I should have invested in a harness a long time ago but I wasn't sure if I'd be really bitten by the rock climbing bug. And, oh boy, have I been bitten. I miss the wall almost as soon as I step out of the gym.
I finally managed to get up the 5.8b (a.k. a. #1 nemesis) And You're Ready Now? route. It took me many takes and I don't really know how I made it over the arête but I did; I'm hoping that my muscles will remember. I was sapped after that 5.8b and could barely muster enough energy to make it up less demanding routes. Nevertheless, I was quite satisfied to have finally made it up And You're Ready Now? Yay!!!
Here are some videos about how to look for a harness and how to put one on.
On a final note, looking at my, woo hoo, smaller butt makes me think about Greta over at Big Bottom Blogger.
And, of course, Da Butt also comes to mind.