It's easy to reset your universe using GameServerKing's Game Server Management Panel. First, login using your TCAdmin password, which was emailed to you with your verification email. Then, go to "Game Services" using the navbar on the left and select your Starbound server. From there you'll want to click the "File Manager" button.
Now that you're in the File Manager, make your way to the "storage" folder. Within, you will find another folder titled "universe", click on the checkbox next to the file. From this point, we recommend that you save a backup of your universe folder, as it contains all of your map data. To do that, click "Create Zip" and then click on the earth button next to the newly generated file to download it.
After you've downloaded your backup, all that's left to do is to click on your "universe" folder, and check all of the files inside. Once selected, press delete. Go back to your main server panel, and hit refresh. Now, Starbound will auto-generate an entirely new universe for you to play!