Pick the desired cross-sections from the list in the cross-sections area of the tab.

The Cross-sections section lets you specify the cross-sections from which you wish to calculate resultant force and moment results for each selected loadstep.  Cross-sections are created using the Cross-section Manager.  Multiple cross-sections can be selected by Ctrl-clicking and Shift-clicking.  The list can be filtered using the buttons provided, including a name filter that uses standard Engineering Solutions filtering syntax.