You can identify the muscles located around the bladder opening by starting and stopping your urine stream. If you are able to stop mid stream, you’re using your pelvic floor muscles.
Another way to identify pelvic muscles and complete your pelvic floor exercises is to tighten the muscles around your back passage (as when holding back wind or at the end of a bowel movement).
A proper pelvic floor squeeze also works to lift the engaged muscles upwards. Use a hand mirror to see if you can notice any upward movement when you contract your pelvic floor muscles.