Making your account an admin on TS3 is very easy;
* Copy your admin token from: Clanforge -> Servers -> The grey box under the server details will list your token.
* Open TS3 and connect to your server
* Permissions (menu at the top) -> Use Privilege Key
* Paste your token in here
Your account will then have admin rights on the server.
If you need to generate a new token, due to a fresh install on your PC, then you'll need to do these steps again.