In some states, you won’t need to do any work at all; the lienholder will contact the DMV to inform them of the change, and you’ll receive your title in the mail within a week or two.
In other states, though, you’ll need to fill out some paperwork before you receive your title. If this is the case, you’ll receive a lien release and formal documentation that the loan is paid in full, which you’ll then need to bring to the DMV to get your title.