I want to go from a light brown to a blonde, how do I achieve this?

If it's dyed brown, don't bleach it. It will start to break off, go to a salon for that. If it isn't dyed, then you can attempt to bleach at home.

Good luck

Buy loreal feria... the lightest blonde they have and leave it on approx. 25 minutes... you'll see your hair changing. Rinse out once you get a shade darker then your desired color. Your hair will lighten once washed. Good luck!