You can't. If you want a Mothim, you catch a male Burmy, because only the males evolve into Mothim. They don't even go through the Wormadam stage. Females only evolve into Wormadam.
In Pokemon crater when a Pokemon is at a right level to evolve or when you are holding the right item or evolution stone to evolve it go to "My Pokemon" and on the right side of the Pokemon you want...
Once you reach the required level (usually a few over normal), go to "Trainer HQ" and Click on "My Pokemon". There will be a link next to the Pokemon saying "Evolve Me" (next to the column which says...