First off, this is not required at all since you will get decent amount of traffic to your server with or without promoting it.
There are 9 ad spots on the main page, their placements are being rotated randomly on each refresh.
We use rotation as it is the most fair way to display the featured servers.
How to promote your server?
Once your server submission is approved, go to My Account > Listings and then click the Star icon as displayed below.
Extras:
[Profile] and [Server] badges are permanent. They can be found at the Candy shop. (Shows up after registration.)
Badges are useful only if you plan to stick around. Perfect for hardcore server administrators/owners.
it’s pointless to own a badge if you are just casually releasing a server for a month or two.
May the gods be with you!