How can i get frozen yogurt?

okay so i bought some plain nonfat yougurt from whole foods and it taste sour..ew.i now know tht plane yogurt taste like tht and i put it in the freezer for frozen yogurt but it still tasted sour.how can i make frozen yogurt from this yogurt without a machine.and less of a sour taste lol.it be nice to have a nswer for someone who did this before and know the yogurt.thnx(: