Three options for booking a deluxe villa:
1) Direct from Disney. They'll show up in a search on Disney's booking site just like any other Disney resort. As others have said, though, Disney has limited inventory of these villas.
2) Find an owner to rent from on the
DVC Rent/Trade board right here on the DISboards. Be sure to read the stickies at the top of that board to learn the rules for using that board, and the way that point rentals work, which is very different from a typical hotel reservation.
3) Rent from an owner through a broker like David's Vacation Rentals (
dvcrequest.com). They're probably going to cost a little more that working directly with an owner, but for that extra money you get to work with experienced agents who'll find an owner with the right points, handle the transaction, and provide some financial protection.
If you rent from an owner (options 2 & 3), you'll likely pay a good bit less than booking directly through Disney, but there are tradeoffs. The owner will retain control of the reservation at all times; you won't be able to make any changes like adding the dining plan or room requests yourself, that must be done by the owner. You'll get limited housekeeping services, unless you pay extra for that. Most importantly, you will probably not be able to change your reservation dates, resort or room type once it's booked, and you should assume there will be no refunds if you cancel.