What to Wear to Workout?

I'm psyched to be starting a new fitness regimen with my friend Mona at Studio Melt! You would think my dilemma would be, how sore am I going to be tomorrow and the next day, right? Wrong! I've always been a runner and have no idea what to wear to work out indoors! (naturally I'm stressing out about this!)

Anyone have any tips about cool workout wear? I have some great Nike capri pants, I think they might be OK? HELP!!

Jennifer