It's hard to do a tutorial on hair that brightly colored. A lot of different elements factor in for each individual. And to bleach hair high enough to take that level of color is risky to do at home. Even myself would have one of my coworkers or another licensed professional do it or help me do it. Very easy to over processed and do irreversible damage. I'll see what I can put together, but I'm not promising anything. lol.
Your best option is to go to a salon. At least to get started. Dark hair usually have warm undertones which cancel cool colors (which is why blues/violets turn brown and ugly greens a lot) Once your hair is bleached and colored the way you want it's fairly easy to maintain. Roots are the only thing you have to bleach to keep your color up, and I can give plenty of tips on keeping color fresh and longer lasting.