you have to pass the herbology level first... i don't really understand it, you can't get to the herbology level until you've passed the prefect's bathroom, but you can't pass the prefect's bathroom until you've got herbivicus :S

herbivicous you go to the character cards and purchase it

wat if u have the card and dont know how to use it and u cant get back into the first
level?

Just press a bunch of keys and see if you use it