Quick answer, you don’t!
In all spins the lady should be on the balls of her feet. Ask any teacher to demonstrate or watch an advanced dancer.
The piece of paper between the legs is to help increase awareness to try and keep the legs and consequently feet close together.
The confusion you may have is possibly due to the description of the feet being toe to heel in alignment when stepping or doing travelling spins. In other words keeping the feet close together when stepping. Not the placement of your weight on you feet which should always be ball first.
Hope this helps, if you’re still confused ask your teacher, should only take a minute to help you out.