Fitting is suggested during your period as it is meant to be easier as cervix is slightly open.
I had my first one inserted four weeks ago, I am one year post meno so was obviously not done during a period. Even though my cervix kept hiding and doctor had to use cervical dilators it was nowhere near as bad as I expected😀
Mine was fitted as the progesterone part of HRT, I use an Estradot patch for the oestrogen.