It is... drop in your part. Now you will have the two pieces. Click away and then click on the piece that you want to rotate and then click on the yellow dot on the hinge. If the movement gizmo jumps to the hinge and your piece is still highlighted red then you have the right point selected.

Now you can rotate in a few different ways...

With the on-screen gizmo:
If you see the arrows gizmo, switch to the rotation gizmo. Keyboard shortcut is [M] to switch from translate to rotate and back. Think M for Movement type. Now that you are here, you can switch your Transform grid from medium to small. Keyboard shortcut is Q. It will toggle from Medium to Large to Small and back around. At the default of medium, parts rotate at 22.5º increments. If you go to small, you can move in 0.5º increments.

If you don't want to use keyboard shortcuts, you can switch between the Transform Grid sizes at the top middle toolbar. Just to the right the next two buttons will change the gizmo to translate and rotate.

With the Move tab:
Select the part and pivot point as you did before. Look for the Move tab. It is in the right hand sidebar under the Graph tab and to the right of the Object tab. Select it. Under movement type choose rotate. For this part you will want to choose the X axis. Now type in the number of degrees you want to rotate and hit Apply.

Of course, there are a few more ways to rotate parts, but these seem to be the most relevant to your question.

Cheers!

That worked! Thanks!

This is similar to an online videogame "map" designer that I've used. Mainly how it works– the arrows and the rotation tool.

👍

On a similar issue– do you know what happened to an earlier version of that part? It looked exactly like it except that the lower half was 4 studs longer. Did Lego phase it out?

My original version of the MOC I'm working on used that part, and I can't seem to find it in the Part Manager.