When the Analysis Mode = Steady State Groundwater or Transient Groundwater, the Compute (groundwater) option in the toolbar or the Analysis menu, will run the finite element groundwater seepage analysis.
When you have run the groundwater analysis with Compute (groundwater), then you may either:
Select Interpret Groundwater, to view the results of the groundwater analysis.
Or you may switch the Analysis Mode to Slope Stability, and Compute the slope stability analysis. The slope stability analysis will automatically utilize the results (pore pressures) computed from the groundwater analysis.