I assume you want to reset the codes in the remote and opener unit for security purposes. Most systems use dip switches in the remote and at the controller for the opener. The 8 to 10 dip switches are numbered and are either on or off. Both the remote and controller switches must match in order to work. The switch settings in the remote are usually accessed by opening the remote battery cover or a cover plate. The switches in the opener are usually visible near the back or side of the opener unit power-head. Without a brand/model, that’s about all I can offer.