Make a mark on the board where the tenon will be located. Attach tenoning jig to the table saw. Lock the board in place on the jig. A tenoning jig locks a board against a plate and holds it tightly in place so it can cut cheeks and shoulders on all four sides of a tenon. A stop piece keeps the board square in both directions. Cutting on all four sides of a tenon allows for a better fit, thus making the joint easier to conceal. Turn the fine adjustment knob to line up the marks on the board with the teeth of the blade. Lock down the jig and set the height of the blade for the tenon.
Cutting is a two-pass process. Cut one side of the tenon, then the other. This defines the edges of the tenon. Another way to do this is to determine the size of the tenon and plane a board to the thickness of the tenon plus the thickness of the blade. Then you can use that board as a spacer for the first pass of the tenon. The board automatically spaces to the right size tenon. Take the spacer out and make the second cut. The two already-cut sides have created a structural tenon. For a cosmetic tenon (a tenon that has four sides cut out for easier concealment of the joint), turn the board sideways and cut the cheeks of the tenon. (This will require two passes.)