Like others I was also given a book by my mother, when I was about 9 or 10 years old, (which I did not read). Sanitary towels were always in our home, as my Dad suffered from dreadful piles which often bled copiously and he used these when that happened.
Think my Mum must have talked more to me, as I was quite ready when it happened. My Mother was so embarrassed about anything like that, but I was given that belt, and those looped towels to wear. Started on a Saturday, remember that because I used to go all day Saturdays to dancing classes and can remember my Mum saying I did not have to go that day, but I wanted to.
Sadly I did not find tampons until many years later.
With my own daughters we talked about such things often when they were small and they played with tampons in their bath, watching them swell up when they got wet. They were encouraged, by me, to know all the parts of their bodies . All were very involved in sports mainly diving, swimming and gymnastics, so it was important they were happy to use small tampons right from the start. Being very physically active also helped to ensure they were unlikely to suffer much in the way of period pains.
No idea about my g.daughters, although, all but the very youngest have now reached the ages of starting these. Assume they, like their Mothers, were all very well aware