How To Dance For A Wedding?

I am going to a wedding in November, close to Thanksgiving and it is my mother's half brother's wedding and she wants everyone in my family to go and she wants me to go to the wedding reception and dance. Because the last wedding I went to, I wouldn't dance because I can't dance and I told her that but she still said that I have to dance. So, does anyone know how you are suppose to dance at a wedding? Because I do not know any dance moves and I honestly can't dance unless I have a dance instructor, but I am not allowed one. I do not want my parents advice on how to dance, not unless I am extremely desperate. So, does anyone know how you are suppose to dance at a wedding??? Anything will help me! This also might help, I am a 13 year old girl. I have a younger (not older) sister. She is my only sibling.