Message Center

I am trying to use the message center. According to the help file you can do 3 types of notes:

1. For yourself (indicated by a key)

2. To another user by clicking on the push pin next to their names (shows their name and different icon)

OR

3. Subscribing to Notes on a record and seeing any new note added in your message center.

from the help file

Notes on records to which you subscribe. On record types that support the notes feature, you can keep track of conversations about a particular record, by navigating to the Detail page and subscribing to any new notes added on the record. You will then get a copy of all such notes in the Message Center, and you can reply to the record from the Message Center. You only get a copy of new notes added to the record; you do not get notes about other changes to the record.