Requires a new deed to be filed with the state/county where the DVC Resort is physically located. If you call DVC, they will recommend a title agency that will charge $400 US or more. There's a company called LT Transfers that can do the paperwork and filing and their fees start at $175 US.
I did add my adult children in 2019, but we felt comfortable doing it and decided the risks of it being caught up in something like bankruptcy, divorce, etc. was small in relation to them and where they were in their lives at this point,
Be sure you understand all of that. As a deeded owner, they have all the rights you do to make trips, etc. and will have their own DVC log in account.
As mentioned, there are financial implications to doing it so research those too.