This really is not as hard as you may think, although quite time consuming. I had some grapes in my refrigerator for quite a while and just could not seem to get rid of them, so I figured no better time than now to make some jam.
Started with fresh grapes:
Covered and simmered for 7 minutes and then too the cover off and began to boil:
Then I added sugar, 3/4 of a cup for every cup of grapes:
I read to do a taste for doneness you place a plate in the refrigerator. Take a spoon full of the jam and place it on the plate. Put it back to cool for a couple minutes. Push on the jam, if there are creases it is done
So then just take it off the stove and pour into mason jars. The recipe I found said to let cool for a couple of hours, then lid and place in refrigerator.
I found instructions at this site: Snap Guide.