If making jelled cranberry sauce, return the sauce to the stovetop and bring to a boil. Add in a package of Sure-Jell for each 4 cups of cranberry sauce. Boil for just a few minutes, skimming the foam off the top. Process in a water bath canner.
You can absolutely prepare this ahead of time. I make this a few days ahead and store in the refrigerator in a mason jar with a twist top lid. The day of, I remove from the refrigerator, remove the lid, and add a serving spoon. Done!