Kegel Exercise Help

Can anyone give me a clear guide with Kegels? Specifically reverse kegels?

I feel I can definitely do kegels as itโ€™s the same action as stopping yourself from peeing, but the reverse kegel throws me, mainly because it feels like I should be breathing out and not breathing in when doing one.
And there seems to be some confusion on the internet about tensing your bum and your pubic area at the same time, almost like your sucking your penis in?

Thanks