How can I make my Prom dress look formal?

I really wanted to buy a formal one but that's just not me...but I'm having trouble making the one i did buy look formal enough for prom. Please suggest anything. http://www.onestopplus.com/clothing/Blue-Pinstriped-Embroidered-Hem-Tube-Dress.aspx?PfId=234837&DeptId=11583&ProductTypeId=1