I've not canned this jam. Jam isn't so fragile and will keep for several weeks or months, especially if you refrigerate it. If you want canning instructions for jams, you can find them
here (PDF.)
If you only have 1 pound (450g) of cherries, you can cut the recipe in half. The liqueur is optional but it heightens the flavors of the jam. Use only enough so it complements the fruit - you don't want to overwhelm it.
Note that
this jam will be on the runny side, which is normal. Sour cherries will produce a softer-set jam than sweet cherries, but either will be delicious...or do a mix of both. If you want a thicker jam, increase the sugar to 3 cups (600g).