In addition to what NicoleP said; you will need to log out first. Than as she said and click the contact us link at the bottom of the web page. Select Ban Appeal and fill out the form. The Email associated with the account will be mailed with some info on why and when the ban period will end. Send a reply to that email if you have further questions.
While you may have played DDTank on other sites, each web site has their own rules. If you are unfamiliar with AGE's Terms of Service then I suggest you look Here
for a refresher course of AGE's rules.