If you don't have a wikia account yet, you'll need one. To do that, go to the top right, and click 'register'. Then, fill out the form presented. Keep in mind, your username does not need to be and shouldn't be the name of your character. It shouldn't include any personal information either. Instead, try to come up with something interesting, or use a username you use for a different service, such as e-mail. When you are registered, move on to the next step. Also, DO remember your username and password to prevent further problems with your account and wiki activities.
There are other wiki's that allow "anons" to edit, an anon is someone who doesn't have an official account so instead their edits are tracked by their ip address. However, on this wiki due to the way our policies work, we require anyone who wishes to join, to have an account and be signed in. This way we are better able to track users and their characters.