It seems we must disable the Simulation Add-In in order for materials properties to work, which is crucial for simulation to work. To do this, go to Tools→Add Ins, and uncheck the Simulation entry.
Use SI units for this entire lab. Select mm (rather than m) as the base unit (Options (settings gear)→Document Properties→Units→MMGS).
Now draw a part you want to model. For testing, you can just make a simple rectangular beam. Or you can open the Simulation Tutorial and open the tutorial part provided if you want to follow the tutorial more closely.
Set the material (seems to only work if Simulation Add-In is disabled) by right-clicking in the design tree under "Edit Material"—also a tool on upper tool bar for this.
Be sure to save the part before moving on to simulation
Go to Tools→Xpress Products→Simulation-Xpress
Click Options on the welcome screen to select SI units, designate a destination for results (recommend making folder within Desktop), and also check the (useful) "show annotations for max/min" box.
Following the wizard, add a fixture, and select the face or faces that are to be held fixed. Note that a useful trick for selecting a surface that is hidden from view is to right-click on the region, pick "select other" then select the desired surface. This lets you access faces behind the visible ones.
Click the green check mark when done.
Note that the simulation tree at left now has a fixtures entity that can be later modified/edited.
The wizard should now permit the addition of a force. Select the face to which the force is to be applied (default is normal to face, but does not have to be).
Pick a scale for the force that is reasonable—maybe guided by the weight of the part.
If applying a force that is not normal to the surface, use the drop-down tree in the upper left of the drawing/part window to select a plane for the force, and reverse direction if necessary.
Click the green check mark to accept forces.
Note that the simulation tree at left now has a force entity that can be later modified/edited.
The wizard should now allow you to run the simulation, so do that.
Stop the annoying bouncy animation, once getting your fill. Note that the deflections are grossly exagerrated for the benefit of making them easily visible. The animated deflection amplitude is the same no matter how tiny or large the force, within the linear regime.
The simulation tree at left has various results that can be examined (double-click each). Note the max and min values and the scale bar. Trust the numbers, not the possibly-exaggerated graphical values.
Of interest are the stress map, the displacement map, and the safety factor map. For the last one, higher numbers are good: indicating operation well within stress limits.
When done viewing results, you may find an option to generate a report. This is voluminous, so don't just dump this into the final write-up, but it may help you select key info and/or graphics to insert into the write-up.