How do I bleach my hair at home?

If you've never bleached your hair before, I would suggest going to a professional and having them do it, specially if you have dark hair or previously dyed hair. 
Get bleach powder and developer from a beauty supply store. 

Read and follow the instructions carefully, never leave bleach on your hair for longer then the instructions says to, also mix the powder and developer as directed.
Wear some old clothes that you don't care about getting stained, also wear gloves and don't use anything metal, your mixing utensils should be plastic and or ceramic.
After you bleach your hair use a hair toner to remove any brassiness, and use a deep conditioner after you bleach it and after toning your hair.  
There's a bunch of you tube tutorials around on bleaching your hair at home, try watching a few of them before you do it. 

Get a bleach kit at the store. Put the bleach in for an hour. It will bring it down to a orange or yellow color. If it is orange wait a week and rebleach and keep it in for an hour. If it is yellow rebleach after a week for 30 minutes. My hair is dark brown so I bleached it for 1 hour. I got down to a bright yellow. I waited one week then rebleached my hair and left it in for 30 minutes and now it's a light blonde In between bleaches make sure you deep condition once or twice before bleaching again. I did this and it was 20 dollars total. Try to stay away from splat hair bleach it made my hair itch and burn real bad. So I used a different hair color brand and I didnt have any issues with the other brand. Make sure when you get hair bleach it is the. One that turns white while bleaching so when you wash it out you wont have blue bleach mixture **** you gotta clean. Make sure you bleach in a well ventilated area