Pour milk into a medium saucepan and heat on medium low, stirring occasionally until bubbles begin to appear around the edges and steam starts to rise from the surface. Temperature of milk should be 185-190 degrees F (check this using the provided thermometer).
Remove saucepan from heat and check the temperature using the provided thermometer sitrrer. Let milk cool until it reaches the "Add Starter" level—(110-115 F). Add 1-2 heaping tablespoons of starter (ie; commercially prepared yogurt, or dried yogurt culture) to one of the provided yogurt cups, add some of the warm milk and stir until well combined. Pour mixture back into saucepan and stir again.
Distribute milk equally among jars and cover each tightly with their plastic covers. Place yogurt cups into the yogurt machine, plug it in and set it for 10 hours for the first batch. For future batches, you can set it for more hours in order to produce a thicker consistency. After yogurt is finished, it must be chilled for 3-4 hours before serving. Plain yogurt will keep in the refrigerator for 10 to 14 days.