Menstrual cup?

Lamia • My cats are my life 🐱
I'm very interested but very terrified of the Menstrual Cup. I have a few questions.
How do you use it?
Can you use it in the bath/shower?
Can you sleep with it on?
Is it uncomfortable?
Does it come in different sizes?
I would search it myself but family computer and annoying family -.-
Thanking you all :)