How do you get dragonballs in dbz raging blast

Go to the battle trial thing and do one of the things there, if you win and/or get a highscore (depends on thing being played) you will unlock a dragonball battle once you play it defeat the opponent and get a dragonball battle will dissappear and you have to repeat the process to get more and when 7 are obtained instead of "dragonball battle" there will be shenron then chioces will show and you pick one to get it