How do you use a diaphragm?

Dr Rosemary Leonard

A doctor or nurse will examine you internally and advise on the correct size and shape that would suit you. They will show you how to put in and take out the diaphragm or cap. They will also show you how to use the spermicide. This must be used every time you use the diaphragm or cap. You need to be confident that you can put it in correctly over the neck of your womb (cervix), and know how much spermicide to use and how to use it.

https://patient.info/health/contraception-barrier-methods/diaphragms-and-caps