If you squint you might be able to see it in the photo below. There is no connection at either end. The rib rides just above the longeron and almost touches the baggage bulkhead.
The procedure I used, given to me by a local builder, was as follows:
Draw a centerline along the flange on the rib through which the rivets will go.
Using a piece of 1/16" thick aluminum or similar as a shim on the longeron below the bottom end of the rib so the rib won't touch the longeron, force the rib into place inside the skin.
Line up the centerline through the bottom pre-punched hole in the skin, then drill and cleco.
Repeat the process as you work your way up the rib, lining up the centerline through the holes, then drilling and clecoing.
You will have to twist the rib as you go, and you may have to trim the top end a bit, but don't do so until you have worked your way to the top.
Holding the ribs in my hand it looked like there was no way they would fit, but in the end they fit well.
Good luck!