Turning the sand plums into juice can be found in this blog post.
I'm going to start off by apologizing for the quality of the pictures. Since my real camera died on vacation, I've been having to make do with my phone camera - which takes good pictures outside, but not so much inside. Still, you can get the general idea of what we did. I think.
Start off by putting the jars in the canner and the bands/lids in a pot. Boil them both. It takes approximately forever for the canner to boil, so I usually prep everything else while I'm waiting (impatiently) for it to boil. Seriously, it usually takes about 30-45 minutes to get to a good rolling boil, which is what you want in order to sterilize the jars.
You will need:
5 1/2 cups of juice
Pectin (either one box of Sure-Jell or 6 tablespoons of Ball Classic pectin - I've used both, and have had no issues with either one. The Ball stuff is usually cheaper, but not always.)
7 1/2 cups of sugar
a smidge of butter or margarine (optional)
Dump the 5 1/2 cups of juice into a big pot. Add the pectin to it, stir it up really good, and bring it to a boil. I stir it the entire time because I'm too paranoid that it's going to scorch and be ruined.
Once the juice/pectin combo is boiling, add the sugar to it all at once. Stir as if your life depends on it - it takes some effort to get all of the sugar stirred in and dissolved, but it will happen.
Just be very careful - you do not want to splatter this on yourself (or anything else). It's really hot. And really sticky.
After you add the sugar and get it all dissolved, keep stirring it until it boils. It's got to be a real boil, not just a little simmer. It needs to boil (hard) for a full minute. It will get foamy, but if you add just a smidge of margarine to it (like 1/2 teaspoon) it cuts the foaming down tremendously. I don't always do it - to me, it's a matter of personal preference. You can skim the foam off at the end if you don't like it.
After it boils for the minute, take it off of the stove. Use the grabber to pull the hot jars out of the boiling water and put them on the table (notice the towels) and also get the hot lids/bands and put them out too. Put the lid back on the canner and just let the water continue to boil, because you're going to be using it again. You can dump the pot that had the lids/bands in it.
Use the funnel and fill up the jars. Keep in mind that everything is hot. The jars are hot. The jelly is hot. The pan is hot. Pay attention to what you're doing, because hot jelly running down your legs after you miss the funnel with a ladle full of hot jelly isn't pleasant. Trust me on that one. Honest.
When you have them all filled (leave about 1/4" headspace in each jar), use a damp paper towel and wipe down the threads and the edges of the jars - you don't want anything sticky on them or they won't seal right. Then put the lids and bands on the jars and tighten them "finger tight" - in other words, snug, but you don't have to use brute strength to put them on the jars.
Transfer the jars back into the still-boiling water in the canner, make sure that they're covered with water, put the lid back on it, and let them boil for about 10 minutes.
Use that 10 minutes to clean up some of your mess. Trust me, you'll be thankful that you did.
After the 10 minutes is up, you can remove the jars from the canner. Use the grabber to do it, and sit them back on the towels on the table (or whatever you used) to cool.
Again, remember - everything is hot. Really hot.
At this point, you're basically done. You'll hear each jar "tink" as the lids seal on the jars - sometimes it'll happen immediately as you're taking them out of the canner, and sometimes they take their sweet ol' time. I just love listening to the sounds of the lids tinking as they cool - each "tink" means that another jar has sealed and is good to go! I've found that the jelly jells fairly quickly - usually overnight. But sometimes it needs to sit for a few days before it fully jells.
If a jar doesn't seal, just stick it in the fridge and use it. It's fine. As long as they're sealed, you can store them on the shelf just like any store-bought jelly.
One batch usually makes about 10-11 half pints, or about 6 pints. It varies, so I usually try to boil at least 1-2 extra jars and lids just to be safe.
Don't forget to admire your handiwork for a few minutes when you're done.
And that's all that there is to it. It sounds difficult, but it really isn't. It's more time-consuming than anything else. We had the juice already made, and it took about 2-3 hours to make the 3 batches that we made last night.
If you make it, let me know how it turns out for you!