Try your tenon in the corresponding mortise, look for the faces you marked with the triangles earlier on to show you which mortise they go into.
If your stub tenon joint is still a bit tight, use the plane to take off a few shavings off the back face of the tenon. Only take 2 shavings off at a time as you don’t want to make it loose.
On the through tenon for the middle rail, it may be too big to go through the mortise as we left it slightly fat. Use the router plane to get down to the gauge line, keep testing it in the mortise hole until you get a snug fit.
Dry assemble the shelf to test each of the joints and ensure that you know how the project goes together.