You can contact MS - they have reportedly been offering $55 - $58 per point for existing contracts (at least for BCV).
Otherwise, you will need to find a buyer and then submit an accepted offer to Disney for Right-of-Refusal where they will either allow the sale to continue or purchase it themselves for the same amount offered.
If you don't have a buyer already, you might consider a resale broker (The Timeshare Store is the sponsor of this site and has assisted many here with buying and selling DVC contracts.) They can assist with all details of the sale including submitting documents to DVC as well as closing on the deed.