If you go to your profile page, you can see a dropdown menu to change your role. there's lots to choose from even when you first join!

On your user page: https://www.planetminecraft.com/member/mythicalstarz/
click "Profile"(should be at top right just to the left of "My Content" and just under the banner)

In "AVATAR & STATUS" look for "Class" and click the dropdown "v" and you should egt an alphabetic list o fthe options available to you.

Full list by levels is at www.planetminecraft.com/members/levels/