How to Blacklist a message sender?

  I see that there is a 'blacklist" page but I do not have instructions on how to enter a message source into the blacklist page.

This is the information I copied from the manual.  It is to block MMS only.

Blocking a phone number from sending you MMS messages
If you do not want to receive MMS messages from a particular sender, you can add the sender’s phone number
to the MMS Blacklist.
When you receive a new MMS message, open and view the message.
To avoid receiving MMS messages from this sender next time, tap Menu > Show > Contact Details.
Tap Menu > Save to Blacklist.
Tap Done.
Tip To unblock a phone number and allow the sender to send you MMS messages, remove the number from the
Blacklist. Go to the SMS / MMS Inbox, tap Menu > MMS Options > Blacklist tab, tap and hold the phone number in
the Blacklist, and then tap Delete.

Hope this helps.