Belting tunics on petites

I recently got a lovely summer tunic, long and white and diaphanous. But it's so big that I can't wear it with shorts, since it comes down nearly to mid-thigh. I thought I might try to belt it, but I am a size 4 petite with an hourglass figure and don't know where to put the belt so I won't drown. Please help, I really want to be able to wear this!