Instructions
Open the tool menu, and select the Post Office option. It is listed between Watering Can and Encyclopedia.
Buy a crate from Fanny Franker at the Post Office for one chocolate coin. Only one crate is allowed in your garden at a time.
Choose an empty spot in the garden, and press the "A" button to place the crate.
Place the cursor over the crate, and press the "Y" button to select pinata animals and items to pack. Press the "A" button while hovering over the subject with the cursor to pack it into the crate.
Press the "X" button while the crate is selected to display the crate options. For example, you can add a message or chocolate coins, or send the crate away.
Select the Send Crate option to ship the crate. Choose the recipient's Gamertag from your list of friends. The crate will be sent to the post office in your friend's saved game of "Viva Pinata: Trouble in Paradise."