To get started de-stem and wash your crab apples...
Then, put them into a big stock pot and put in just enough water to cover them.
While your crab apples are cooking (you will want them to get to a boil and then turn the heat down to a simmer and cook them just until they are tender), get your jelly strainer bags ready. I use ones that have a draw string, so I didn't need to buy the stand. I just hang mine from the cabinet knob and put a bowl under them to catch the juice.
When your crab apples are tender, scoop them out and put them into your jelly strainer bags and then pour the water/juice that is left in the pot, right into strainer bags and let them strain/drip out their juice.
If you boiled your crab apples at night and loaded your strainer bags then you can head to bed. If you are like me and you are doing it all in the same day, then you should let them hand and drip for an hour or two, then squeezed the bags to try and get all the juice out.
Once you've collected all the juice into the bowls poured it into a large measuring pitcher. Now your ready to put the juice back into the pot and boil it with some sugar. For every cup of juice you will need 2/3 of a cup of sugar. Then boil (a good rolling boil) the mixture fro 10-12 minutes.
Keep those jars hot in the dishwasher until you're done boiling the mixture, then, take them out a couple at a time and fill the hot jars with "jelly juice", screw on the tops and turn them upside down for five minutes. Then flip them right side up and set them aside to cool on the counter overnight. Don't worry, they won't look like jelly yet. Come morning you will have delicious Crab Apple Jelly.
Oh, and if you have any problems with your jelly jelling then, check out this site