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.