Little simple tutorial to vote.. I'm not 100% sure but it's basically what I understand.
http://www.ntv.co.jp/best-artist/
When you are on this page, click on the red button.
After that you have a popup screen and you have to answer few questions :
1) You have to write the names of 3 different artists who, you think, are good representatives of the current Japanese music.
2) Write the name of your favorite song of the artist you like (1)
3) Write any question you would like to ask of your favorite artist.
4) Write the name of 3 new artists you like (rising stars)
5) Write any collaboration work you would like to see.
Then you have to fill the other blank with your personal informations (User name, age group, male/female)
Then clik on the first button to submit.
You'll normally see a blue message after that, it means thank you and means you're finished ^^