did you get your elements visualized in post view? If not, I try to help you to get rid of your obstacles.
Therefore some questions:
1. Sometimes you have to activate specific elements in Post processing navigator in your active Post view in Fringe Plots => Viewports. There you can see element collectors for elements found in OP2 and loaded SIM.
2. When you wrote that you only can select velocity, what kind of result did you expect?
3. What kind ofsimulation solution did you activate - NX NASTRAN SOL 101 - Linear statics?
4. What kind of output requests did you activate in Case Control?
5. Which version of NX do you use?
Please try to describe you model and intentions a little bit more.