Did you already read the documentation of both Vbulletin and www.no-ip.com ? Beacause it is all written there.
- Just search for the readme file in your VBulletin package, or do it here:
http://www.vbulletin.com/docs/ .
- No-IP has it's own support over here:
http://www.no-ip.com/support.php .
It's not that i don't want to help, but i would just copy and paste the text from there anyway until you realy have a specific problem.