I know this is very basic but it will help many users 
Always make a backup before any edits to your forum.
Open the template postbit>postbit
Find:.
Add new line:.
Replace CyberHackers.org With your Url!
Then Save the template.
This tut took 5 minute's to make it will take 2 seconds to say thanks!!

Always make a backup before any edits to your forum.
Open the template postbit>postbit
Find:.
PHP Code:
{$post['message']}
Add new line:.
PHP Code:
<br><small>© 2010 - CyberHackers.org</small>
Then Save the template.
This tut took 5 minute's to make it will take 2 seconds to say thanks!!