Find your PC muscles sitting on the toilet. While urinating, practice constricting the muscles in your pelvic floor to stop the stream of urine. This may take several practices, but attempt to stop and continue the flow of your urine several times when you need to use the bathroom. This in itself helps in strengthening your PC muscles.
Sit comfortably on your couch, bed or even a yoga mat, if this is what you prefer. After you've practiced stopping and continuing the flow of your urine, you should be aware of where your PC muscles are located, and how to tense and release them. Practice finding your PC muscles in the same manner, but attempt to hold the tightened position for longer periods of time. This may take practice.
Constrict and release your PC muscles anytime. When you're in your car, at your desk or standing and preparing a meal. Nobody will know you're doing it but you, and once you've figured out how to find and hold the tightened position, your pelvic floor muscles will increase in strength and tightness.