How do you okemon get stronger?

Answer 1

I'm guessing you meant to type "Pokemon." You have to battle them against other Pokemon so they gain exp. The higher level they are, the stronger they are. There are also some items sold at Pokemarts that you can buy and make your Pokemon eat and it makes them gain a level, called Rare Candy. It's not sold at every Pokemart, though. Just the ones in the cities you go into later in the game.