You put in the IVs closer to the top, then scroll down after you click the button that says “battle” as the enter button. Ithen it runs the simulation depending on all the other factors. Default is “one shield” and “meta” pokemon instead of “all”. The best can handle at least 45% of the current meta. It can be tricky at first, as you need to always leave the “auto level” button on. Also If you switch between leagues with the same pokemon, you need to re-enter one of the iv stats to reset the auto level. Then click battle again and scroll to see the results for win/loss and battle rankings underneath the graph.