I don't know how to dance

I feel self conscious trying to dance, and ive always wanted to learn how. Some girls have been open to teaching me, but then the self consciousness kicks in and I give up. I cant keep to the beat or rhythm. It was really awkward when a girl was grinding me on the dance floor, I just stood there because I didnt know what to do. How do I learn just how to basically move and just to be a beginner dance partner?