If I want to set up an attitude for station keeping on the R-bar.
So, you just need to translate your desired task into the tools of the Space Shuttle:
Keep any attitude ==> UNIV PTG, G201 "Universal pointing"
So, you need an IDP/CRT combination which is connected to a GPC using the GNC major function software in OPS2. You select this by the switches on the central pedestral. If you select another major function by the switches, the IDP will select another GPC which is running the software you want.
Now, you can enter OPS 201 PRO in your keyboard, if you need to switch the major function. In Orbit, you usually don't need that, it should be in 201 most of the time.
Now when you see this rather overcrowded display, the important question is: What kind of attitude do you need? By answering this question, can be mentally start to ignore many options, because you don't need them.