1) Click on "Manage Inventory" under the 'Inventory' heading of the Control Panel.
2) Search for your item by it's Item ID or Author / Title.
3) Scroll down to the 'Search Results' and click the 'Edit' link under your item.
4) Click on the 'Amazon Properties' button.
5) Scroll down to 'Collectible Item?' under the 'Collectible' heading. Click 'Change' next to 'Collectible Item?'.
6) Check the box next to 'Collectible Item?' under the 'Collectible' heading.
7) Select the appropriate 'Signed By', 'Dust Jacket Condition' & 'Edition Type' for your item.
8) Scroll down and be sure to click the 'Save Properties' button when you are finished to finalize your 'Collectible' settings.