Ok, its basically the same as a standard battle except, there are the gyms rules you have to abide by as well as standard ruels, most gyms have added ruels, like mine, my rules basically say you can use up to 4 OUs and you cant use Dragons. I also have to abide by that rule as well as the type rule, which is that atleast 4 of my pokemon must be my gym type which is Ice. you get it?