Women use sanitary pads or tampons to absorb menstrual flow. Every package has instructions. Tampons and sanitary pads come in different sizes and varieties. Some are for lighter flows. Some are for heavier flows.
Pads stay in place by sticking inside the underwear.
A tampon fits inside the vagina. The walls of the vagina hold it in place. Each tampon has a string that hangs out of the vagina. The tampon is removed easily by pulling the string slowly. Tampons or pads and regular bathing are all a woman or girl needs to stay clean during her period.