To start, make sure your jars, lids and seals are all clean and sanitized. I like to warm up the water in my canning pot with the jars inside them. This allows them to sanitize the jars and bring the jars slowly up to the heat level needed for canning, without the risk of cracking of a jar from heat exposure. I put the seals and lids in a small pot with water and boil off as well.
Add 1 cup of fresh cranberries to each jar. Then add in 1/3 cup of sugar (or the amount you'd prefer!). Finally add in hot to boiling water to about 1/2 inch of the top of the jar.
Make sure to use a canning tool to push out air from sides of jar, and wipe rims of jars dry. Add the seal and ring to each jar and twist shut to finger tightness. Place in canning pot. Make sure water covers the jars (you may need to empty some water if you sanitized your jars in the pot) and replace lid. Once water is boiling, allow jars to process in boiling water for 25-30 minutes.
Remove jars and place on towel out of the way to cool for at least 24 hours. Check to make sure the jars have sealed and if so, label with date and put away! Able to be stored for at a year to a year and a half.