Select the "Friends" option on your PlayStation 3.
Open the "Message Box" option.
Select "Create Message."
Choose the option labeled "TO:" to pick a recipient for your message. You can choose from any PlayStation Network user ID that you have ever met in an online match. Select their name by pressing "X." The user ID is the screen name the player uses during games on the PlayStation Network. This is not their actual personal email address, but the user ID associated with their PlayStation Network account. This is the address they use to receive emails via the PlayStation Network, not via a computer.
Type your message into the main message window using the controller and select "Send." When the person responds to your message, select "Add as a Friend." This will add their PlayStation Network ID to your "Friends" list via their PlayStation Network email account.