How do you vault boost from gifts in Mafia Wars?

Answer 1

If I understand your question right, from the main page (or anywhere really):

1. Click on "Inventory" in the bar with Home, Jobs, Fight, Properties, Inventory, and Godfather on it.
   
2. On the next page, click on "Collections & Vault" in the bar that's a little lower down on the page and contains the items Inventory (Mafia Store), Loot, Collections & Vaulting, and Gifting.
3. On the ensuing page, scroll down, find the collection you're trying to vault, and, if you have all 7 items, click on the "Vault Collection" graphic on the right hand side of the collection. If you have all 7, the Vault Collection graphic will be lit up. Otherwise, it will be dimmed.
   
4. Once you vault a collection, you have the option to revault it to gain whatever boost is associated with that particular collection once you complete the collection again. The first vaulting uses up 1 of each item in the collection, so you'll have to recollect each item to revault the collection and gain the associated boost.