You will be able to get your Custom Title once you have been on the board for 30 days. There is no posting requirement to have a custom title.

Please Note: Every once in a while the board has a bug where it will tell you that any Custom Title you pick is too long - even if your custom title is only 1 character. When that happens, just PM gondee - he has to reset some settings on the board to get it to work again.