How does croagunk evolve into toxicroak?

Croagunk evolves into Toxicroak starting at level 37.

There are several ways to get Croagunk to level 37:

1) Train Croagunk to level 37 by having it battle.

2) Leave it at the daycare until it reaches level 37. It will not evolve while in the daycare, however.

3) Use Rare Candies on it to raise its level.