Ask the staff for the Riordan wiki, not people here.
However, the only way you can become an admin is if you are promoted by another admin in the Riordan Wiki. You can adopt some wikis which lack active admins, but this does not apply to Riordan Wiki as far as I remember.
You won't be able to adopt cuz there are active admins, and you are very unlikely to be given adminship if you ask right now because you barely have any edits on that wiki. Keep editing, then maybe you can ask to be promoted. :)