You can use a point that you created in the model, or you can create a point within the Mechanica (Simulate) model that won't show up when you exit Simulate.
It's under Refine Model (in English at least), and the drop-down gives you different ways to create it - I most often use Offset Coordinate System.
Note that I believe it's important to create the point outside solid geometry, otherwise it stops being a point (with 6 degrees of freedom) and becomes a node of an element (with only 3 DOFs), and then you can't apply moments to it.