Either or- you can find a mentor first if you'd like to, or just make the character and look for a mentor afterwards. It's best to look at WindClan's warriors before making your apprentice, since it's best for apprentices to be paired up with mentors that have the same element (although this doesn't always happen).

For your first character, you can choose from any of the main four elements, Fire, Water, Earth and Air. For a second generation character (born from a litter where parents have been roleplayed and the character is adopted from the litter), it’s genetic. Say for example, your characters mother is an Air elemental, while the father is a Fire elemental; your character has a chance of being a Storm elemental but I believe there’s an item in the shop that increases the odds of getting a combination element