I recently got my first server and got this and a few other plugins. It has me registered as a guest on the server, but I'm the owner. How do I change this to allow myself to other commands?

Aww there's no need for you to be so upset, how do you not know that PermissionsEx is extremely out of date and useless?

Use LuckPerms :)

luckperms won't cure an unwillingness to read the manual but sure