How much Weight can my Frame hold?

I am designing an aluminum frame for a second level on a pontoon in Solidworks and I'm curious to how much weight it can hold.  I know my way around Simulation but I don't have a lot of practice applying it.  Was curious to see any input on the best way to simulate a load being applied to the top of this frame, in order to find out how much weight it can hold before failing.

SolidworksSimulation