Use: /msg NickServ REGISTER <password> <email>
Example: /msg NickServ REGISTER s3cur3P@ss you@example.com
Quick: /msg NickServ IDENTIFY <password>
Tip: enable SASL in your client for auto-login.
First join/create the channel:
/join #yourchannel
Then register it:
/msg ChanServ REGISTER #yourchannel <password> <description>
Example:
/join #EYErc
/msg ChanServ REGISTER #EYErc s3cret "Official EYErc.net channel"