It depends on what you are looking for, you can either do AC or S parameter simulation. To visualize the effect of the capacitors value you can either use "tune" or a parameteric sweep.
To tune click on the tuning fork icon and click on the capacitor. Then you should see the simulation result and how it changes when you change the slide bar with the capacitors value.
The second option is to use the parameter sweep controller. In order to do that you need to declare a variable to hold the capacitors value (var icon). Set the variable with some initial value and then assign it to the capacitors value. It should be something like "C= MyC pF" note that the units are in pF's, you can obviously change that.
After declaring the variable setup the parameteric sweep controller to sweep the variable (you will also need to point the controller to your main simulation controller)
I hope this is clear enough, I typed this from my phone. If it's not clear enough say so in the comments and I'll edit the answer from the pc with screen shots.