How to make this white dress into a prom dress

I would say that dyeing it would make it look far less wedding-dress like. Maybe a deep red. Depending on the fabric, it should dye with RIT or another similar brand. There are special dyes made just for polyester fabrics; RIT is mostly for natural fibers. I think what would make it look less like a wedding dress is to take off enough tiers of the skirt to get rid of the train. (And don't wear a veil, lol)
Wearing a shrug would probably also give it less of a wedding look.
If you're going to wear black studded shoes, maybe make a black studded sash for the dress, and stud a blazer (or maybe just straps) for the dress. If you want something that goes more with the jewelry, make a sash to match the jewelry you'll be wearing.

I think if you change the colour it wont look wedding-like at all. As Monika said, a deep red would look really good. If you take off a few layers of ruffles it'll not only make it less weddingy but it'll most it a bit more practical (you don't want people standing on your dress all night). With the red jewellery I think I'd go with black if you were going to dye the dress & different shoes; I know not many people will see your shoes but they don't really go with your jewellery. Some plain black shoes or swapping the jewellery for something that goes with the shoes would work & then you could go any colour you wanted with the dress. Personally I'd keep the shoes, dye the dress black &, instead of the sash, add a thin studded belt then forget a necklace & go for a chunky, studded bracelet & some big earrings.

Ooo or another idea; dye the top half black & the ruffles red or the other way around. Instantly gets you the colour scheme you want & theres enough black to make it so that the jewellery wouldn't make you look like "I'M WEARING SO MUCH REDDDD!!" Whatever you decide to do just make sure you get rid of the train, it'll make it look at lot more like a prom dress rather than a wedding dress & will be so much more practical.

thanks very much for the suggestions
but im worried about dying the dress -__-
Also I dont mind wearing a white dress because its differnt from the sea of red and blacks and blues at my prom. I know for sure the train is going off thugh

White will make it very easy to accessorize. If there will be a lot of girls wearing red, black, or blue, you could always go for a funkier color like green or orange and just do different jewelry.

Dyeing tends to work wonders when you have the equipment for it.

the link for the dress doesn't work

I can't see the dress or the necklaces. I would just play it up with really fun accessories and get some fabulous nail art.