There are a few ways to secure a DVC reservation. You may look on our Rent/Trade board and reply to a Points for Rent thread. Or you can also contact our Rent/Trade board sponsor, David's Rentals.
There are also other sites like Ebay, craigslist, or tother Disney fansites that may offer a place for owners to rent DVC reservations.
Assuming you've never rented points before, I would suggest reading through this thread:
Remember that rental transactions are a private transaction between you and an individual DVC Member, based primarily on trust. Disney/DVC will not intervene on your behalf if there is a problem. And cancellation policies vary from owner to owner, most consider it a final transaction, with no refunds.