How to go to a high school in Japan

I want to know how and what I need to get a student visa or whatever to be able to apply/go to a high school (senior) in Japan in year 11. Such as the paperwork and stuff. (Can you list the procedures and make it simple and not complicated so I can understand)

Make contact with the school and ask you parents first. Your question hints at you not doing these first stages first.

Can you list the procedures and make it simple and not complicated so I can understand

If you think you can come to Japan to go to high school, and you need it to be simple enough for you to understand, then you need to do some more school in your own country before even thinking about doing anything like leaving the country. That statement shows you really are not ready, able or equipped.

As a start, here are some simple steps:
- be fluent in Japanese (because school will be in Japanese).
- read the immigration requirements from the Japan Government websites.
- have enough money to pay for all of your living costs.

That is a simple starting list.

Best easier way, just check 'google' for any high school exchange program available in your country and start from there.
Normally those program will mostly guide and prepare you for the exchange.

With you being a minor, you will need your parent or guardian approval/consent to process some of the documentation.

Read this procedure
http://www.japanvisa.com/visas/japan-pre-college-student-visa