Start by sterilizing jars and lids. This takes a little while, so I start this 1st. I place my clean jars in my canner and cover with hot water. Bring this to a boil and boil for at least 10 minutes. Remove jars when ready to use. Pour some of the boiling water from jars back into canner and keep the water boiling so you will be ready to process jars of jam. In another small pot; sterilize lids in gently boiling water.
Prepare fruit; chop fine. I used my food processer and it works great for chopping fruit. Just don't liquify the fruit. A little juice won't hurt. I hand peeled my peaches but you can remove the skin the same way you would remove skin from tomatoe by dropping a few at a time into boiling water for 2 minutes and then in cold water. The skin should come right off. I chopped the peaches fine and the blueberries coarse. By freezing the blueberries first will help keep from liquifying the fruit when you chop it.
Add the blueberries peaches, lemon juice, sugar, cinnamon and butter to large pot (Butter helps reduce foaming). Over a medium high heat bring fruit mixture to a rolling boil. A rolling boil is a boil that you can not stir down with a spoon. Continue to boil fruit mixture 4 minute once it reaches a rolling boil, stirring continuously.
Turn heat off; stir in pectin. Remove jars from canner onto a dry towel. Ladle fruit mixture into hot jars; cap with sterilized lids and tighten bands. Return jars to boiling water in canner and gently boil for 10 minutes. Remove and cool. After completely cooled, check seals and bands.