@Bill ,
You aren't alone in just learning as you go. At one of the late night sewing sessions I used to attend there was a new lady sewing on a very pricey machine, like the $2,000 USD range, making a racket and skipping stitches. Someone asked when she last changed the needle. Answer was "you have to change them?" The room went
. She then got a little group tutorial which included to read her manual which she had never done either. The salesperson had shown her how to plug in the foot pedal, put the ¼ inch foot on and sew a straight seam. This was like her 7th or 8th quilt. The fabric rose up or down with each stitch.
On their website
Schmetz has great information about needles on their resources page. They also have a needle selector app available.
While you're at it read your manual. It gives you pairings of fabric, needle type and size as well as thread weight recommendations. :thumbsup: