Every timeshare system is different. Some resorts have an internal exchange system and some don't. It also depends on if you own a floating or fixed week. Many resorts also rent bonus time to owners at a discounted price. The first thing I would do is check with my resort to see if they have any internal program for exchanging/reserving different weeks or a rental program. Also, find out what exchange co. your resort is affiliated with.
If they don't, then you would either have to do a direct exchange with another owner, or go through an exchange company, If you only want to go to you own resort for a specific week, it might be difficult.