You'd have to wait for the moderator who banned you to respond to the post, and tell you how long you got banned.
If it's something minor it should be about 2-4 days, if it's more serious about 4-7 days.
If you've destroyed over 400 blocks, it may be a permenant ban, in which case you should really wait
Other than that, try to log on every now and then, and see if the ban time is over yet.