How to change the main class in my profile?

As you've noticed my profile says my main class is pugilist because that's what I took as my first choice when i created my character, But then my highest level now is my Arcanist, and I will be maining it as a summoner. How can I change my profile main class to my Arcanist or summoner? So it will display the appropriate level?

And also, I noticed, i cannot post in other sections because my level is too low, what level do I need to get before i can post in the other sections?

1. Go to settings and character and drop down your main.
2. You must level ingame...it's dumb I know. In order to post more.
Level 50 gets 20 posts.