To get the Bonus Prize Items you must vote for each category the day it comes out (besides the first two Categories which you will have a day and a half). You'll know you've succeeded in voting for the Category the day it came out if it has a dark blue border around it after submitting your vote. If you didn't succeed in voting on the first day, it will have a light blue border around it. This is also how you can get the Premium Bonus Prize Item.