I know i may sound stupid but i can't help wondering...

What is the right was to Mandi Hadas Besar??? & if a woman didn't mandi correctly does this means that her prayers are not counted??? PLEASE help. I'm too embarrassed to ask my family and my friends. I want to know the right way but I'm scared to ask them. Thus, can anyone teach me the right way to mandi hadas besar....???

Thank You