The production of the grape juice is described in the recipe for grape jelly with vanilla butter and cardamom.
Put the grape juice, chilli and preserving sugar in a sufficiently large saucepan. According to the instructions on the package, cook for at least 5-6 minutes, stirring occasionally. Then fill the jam jars, screw the jars together and let them stand on the lid for about 5 minutes, then turn them over.