The pelvic floor is not just one muscle, but many. To ensure you engage all of the muscles during a contraction you need to:
Ensure you're closing from back to front. Either visualise closing your back and front passage, or that your coccyx (sitting bone) and pubic bone are coming together.
Once you've got the close - draw the contraction up. You may find it helpful to imagine you are lifting up a marble with your vagina!!
The lift can be tricky if the pelvic floor is very weak but keep trying and it will get easier.
Claire is a women's health and sports Physiotherapist. She is the owner of Spring Physio and is based in East Sussex.