Here is how you modify your TurnKey WordPress Footer.
First you need to log into your webmin console. Usually https://x.x.x.x:12321 but check your Config Console on your VM appliance to be sure.
I found the best way to do it other than CSS, because non-CSS pages will still have this footer message:
1. Login to webmin using your root account. (From above step)
2. Under the Servers tab go into Apache.
3. Click Default server.
4. Under Per-Directory Options click Location /
5. Click Edit Directives.
6. Delete all the stuff in that box. Save and restart apache/ click apply changes.
7. Reload your webpage, you might need to clear your cache.