Ok here is the first thing you do when you meet someone who also has a blackberry step by step
to find out you pin from the main menu>options>stauts>it will say "pin"
To add someone to your blackberry messanger.....
1. get the other persons pin as I have describe it the first part of this post.
2. Go to address book and go to the persons name and select "edit" then scroll down to where you see "pin" enter the pin in the contact info and then save the contacts info
3. Go to blackberry messanger and hit the option button and select "add contact" and then start typing in that persons name and then it will say somthing like "your request is pending and then the other peron who you requested to be your friend will get a message and it will say somthing like " john smith wants to be your friend" and just select ok and then you are done
Hope that helps out
