The old way of doing it required sterilizing the jars and then processing after you put the jam in. The newer way of doing it (which you can see on the package when you buy your jars
) Is that if the jam will process for at least 10 minutes, there's no need to sterilize them as they processing will take care of this.
Now if you're processing the jam for less than 10 minutes you will need to sterilize the jars first. To do this you need to put the jars in a big pot and cover the jars with water 1" above the top of the jars and boil for 10 minutes. Whether you sterilize or not, you should keep them in a warm oven about 225 degrees. That way you don't risk them breaking from the heat of the jam. IIRC you do not sterilize the lids.