How to create a listing using the "You-pick" or "U-Pick" option?

[olympusmonsvii]

Hello, I sell hockey cards, and wish to create a listing using the u-pick option for a large lot of cards that i dont wish to sell as one bulk listing; many folks like to complete their sets and are in search for specific cards.  i would combine shipping - this is a commn form of listing for hockey cards and trading cards...thanks!