Ladle hot jam into jars fitted with a funnel, leaving 1/3″ head space for processing. Rub the rims of the jars with a damp, clean cloth to remove any splatters. Attach lids and return to the water bath canner, making sure the jars don’t touch each other or the bottom of the pot (that’s what the jar rack is for) and that there is at least one inch of water over the tops of the jars. Bring the water bath canner to a full boil and then process the jars
appropriately for your altitude (where I live, that means 5 minutes–though I boiled for 5 minutes and then left the jars in the canner for another 5 minutes after I turned off the heat, just to be safe). My source recommends processing for 5 minutes for 1001 to 3000 ft elevation, 10 minutes for 3000-6000 ft elevation, and 15 minutes for 6000-8000 ft elevation.