Two ways actually to start, you need a yogurt culture. Some use store bought yogurt with active cultures (read the label) or like we did was to order yogurt starter off the internet. I bought it off of eBay and had it mailed to Belize. We also found some at the health food store in Spanish Lookout. Anyway we even use the powdered milk before we found a cheap source of good cows milk from a local farmer. Anyway
Mix the powdered milk as directed, put in a sauce pan and scald it. You can check the definition on the net for proper directions. After milk is scalded you add the yogurt starter. Then we pour into glass containers, we bought mason jars from the hardware store but you can use anything, just make sure they are the same size. Immediately put them in a cooler large enough to fit all the jars.
This takes a little experimentation as you do not want a lot of wasted space that has to be warmed up by the jars of yogurt. Our cooler fit 6 quart sized mason jars nice and snug. So we adjusted the recipe to fit that amount of milk as we have 3 kids who love yogurt. Put a towel under the jars and then ne on top. Close it up for about 5 or 6 hours until set the way you want. This time varies some with outside temps. Then we add fruit on top of the yogurt for flavor. Enjoy, no fancy yogurt maker needed. It takes a couple of times to experiment to get it right but it is worth it!