Your forums title is based on the amount of points you have. You can get more points by gathering trophies, all trophies are listed here:
https://www.cubecraft.net/help/trophies/. You can find the trophies you already have on your own profile page under the About section. And these are the titles you get when you have a certain amount of points:
Member: 0
Novice member: 30
Well-Known member: 75
Dedicated member: 150
Forum expert: 250
Forum veteran: 400
Forum professional: 550
Forum legend: 704
Forum god: 743
If you have more questions, feel free to ask!