Simple and delicious, here is one way to preserve and use all those blackberries!
In a large saucepan, stir the crushed up blackberries together with the pectin.
Stir constantly, over high heat, while bringing mixture to a boil.
As soon as the mixture reaches the boiling point, quickly add the sugar.
Continue stirring constantly, and bring the mixture back up to a full boil.
Keep at rolling boil for one full minute, stirring constantly.
Remove from heat. Skim off foam, if any has formed.
Fill hot, sterilized half-pint jars. Leave 1/4" headspace. Remove air bubbles. Wipe the jar tops, edges, and threads clean.
Secure hot, sterilized lids with bands and screw in place firmly.
Process in boiling water canner for 10-15 minutes.