After you have registered your nick, the set command allows the settings to be changed. You must identify to NickServ before being able to change any settings.
AUTHORIZE - Require authorization for others to add you to buddy lists.
EMAIL - Change your email address.
FIELD - Set additional information for a nickname.
MFORWARD - Forward memos to a different nickname.
MLOCK - Lock your preferred user modes.
MRECEIPTS - Receive notification when a memo you sent is read.
NOMEMO - Disable memo receive service.
NOOP - Prevent others from adding you to room lists.
PASSWD - Change your nick password.
PROTECT - Set nick protect on/off.
SECURE - Ignore the access list except for determining whether to guest the person.
SHOWEMAIL - Allow users to see your email address.
URL - Change your URL
/msg nickserv help set <topic>