Ok, so because I want what I am knitting (a shawl) to fit and work out as the instructions say it will, I intend to knit a gauge swatch. Hypothetically, my gauge is not the same as the instructions say it should be, so now what? How do I go about adjusting my gauge so that it measures up with the “so many stitches and so many rows equals so many inches”? Thanks.
Shawls don’t need to fit like a sweater so as long as the gauge isn’t drastically different you’re fine.
Answering your other post - you can usually find another substitute fingering yarn, here’s some of the other yarns that were used. If you want to use laceweight instead that’s fine. Lace is usually knit fairly loose so try out the needles suggested for the fingering weight and see how it looks, not so much to get the same gauge. Try a sample of the pattern repeat, or just cast on and work a few inches. Then block what you’ve got done, even while it’s on the needles, and see how it looks. I see that it’s done on a size 4 and that’s not really too big for a lace yarn. If you want to go down in needle size that would be okay, you’ll just need more yardage if you work more repeats of the pattern, or it may come out a little bit smaller.
If you do need to adjust gauge the simplest thing to do is to change the size needle you’re using: too many sts/inch, go to a larger needle, too few, go to a smaller needle. Get the stitch gauge and don’t worry about the row gauge so much. Most patterns have you knit so many inches anyway.