Pokémon Simulator isn't actually a game. The user in reality doesn't play anything, as it's more of a combat viewer between different Pokémon. So you just select the Pokémon you want to fight (together with their different strengths and weaknesses), and watch it happen.
Just as if you were a trainer, you have to choose the Pokémon you want for each combat, then get comfy and watch the fight spectacle.
A program which, above all, will be enjoyed by all Pokémon fans and the strange ways the characters have of combating and fighting.