You would need to bleach your hair and than tone it to a platinum blonde. I would not suggest that you do this by yourself at home. It's best to go to a salon to a person who knows what he/she is doing. Ask your friends who go to hair salons which one's a good one and if they recommend a great stylist to do this. Trust me, you want to pick a person who knows how to do their job well.
I once had my roots bleached by a stylist who apparently had no clue what she was doing. She turned my hair orange and than didn't know how to fix it. Once she kind of figured it out thanks to the other girls working at the salon, she had to bleach my hair twice (not a good thing). She got it close to what it was supposed to she left it as it was. My hair was yellow for a month till I finally learned to bleach my own hair and fixed it myself. I definitely feel bad about throwing away so much money just so some girl can screw up my hair.

Anyway, ask around and get it done professionally at least the first time. Than you can learn how to touch up your roots by yourself at home so you don't have to spend $60+ dollars every month just for that.