It's "/nickserv", not "/ns" (just tried the latter and it doesn't work)
Once you have settled on a nickname here’s how to register:
ns register yourPassword yourEmailAccountName@yourMailProvider
Email address is mandatory.
Get the confirmation code from your email inbox. Type the following command and replace confirmation_code with the code sent to you in the email (NEVER replace the word "nickserv" in /msg nickserv ... with your nick). It has the template shown below. If you don't see our email in any folder (check spam too) you could try /
ns resend .
ns confirm confirmation_code
Congratulations! Your nickname is now registered if you see a message reply containing