Instructions
Turn on your Xbox 360 and press the "Xbox Guide" button on your controller
Press the "Guide" button again, then choose a player profile from the "Sign In" option.
Choose the "Messages" option, then "Create New."
Select a friend. If you are giving Microsoft Points to someone not on your Friends list, choose "Enter Gamertag" to input the person's information manually.
Input the Microsoft Points code, then click "Done."
Choose the "Send Message" option to send your Microsoft Points.