New user questions

I'm a 21 year old virgin and I just got the diva cup model 1. I have no problem getting it in and open,  and it seems to seal up fine. But the instructions say to seal at you have to turn it 360 degree. And no matter what I try I can't turn it. Is this something to worry about or is it one of those things that they say you have to do but you don't have to do.
Also it feels like the grip and the stem of the cup are irritating the skin inside. Is there something I can do about this?
Thank you in advance for your health.
- Jackie