How do I change the switch controlling the light in a ceiling fan?

Turn off the power to the light and remove the bottom cover

Remove the switch and take it to a hardware store to get one

It should be a simple ( ON -- OFF ) pull cord switch

There should be two wires to it -- it doesn't matter which wire

Hooks to switch wires so just one to each switch wire

Ceiling fan pull chain replacement and repair - Ceiling Fans N More