Find the circuit breaker for the room with the recessed lighting. Shut off the the power.
Unscrew the light bulb from the recessed lighting. Use a ladder if necessary. Set the light bulb aside for later.
Remove the metal baffle from the light fixture by locating the springs and disconnecting them from the inner can. Snap the trim away from the recessed lighting. Use pliers as necessary to remove the dated trim from the baffle.
Snap a new piece of trim on the recessed lighting baffle.
Reattach the springs to put the baffle and new trim back in place. Slip the springs into the holes in the baffle. Screw the light bulb back into place.
Repeat the process with the other recessed can lights in the room.