Instructions
Log on to the PlayStation Network via your Network user name. If you don't have one, follow the on-screen prompts as directed to create a PSN account. Also, you'll need a secure wireless router to gain access to the Network's online community and add-on downloadable content.
Load your copy of "Little Big Planet 2" into your console and access the game menu screen. Scroll down to "PlayStation Store" and press the "X" button on your controller. Scroll down to "PS3 Content." Click "Browse All Games, A-Z" on the menu list in the store; click "L" to search for "Little Big Planet 2" and press "X." This opens a new selection of downloadable items.
Browse through the selections to find Ezio's assassin's costume. Hit "X" to select the item, where you'll then be prompted to purchase the item using PlayStation credits or actual money from an account linked to the PSN. As of 2011, Ezio's costume costs $3. Exit the menus to reach your Network profile and click "Install" to activate Ezio's costume for in-game use.