This guy's channel is pretty great for learning all sorts of stuff https://www.youtube.com/@TockCustom

The first main thing is how to thread your machine(s), since that does tend to be pretty similar from one machine to another but with slight differences. So I'd learn how to do that for your particular model(s), how to wind a bobbin and get that all hooked up.

Then just pick up some scrap bits of fabric and go to town with the different stitches and features and see what happens! If something goes wrong, search online for the specific symptom and you'll learn a lot that way (this is how I learned how to adjust tension back in the day).

Do you have a manual for either machine that takes you through the different stitches etc? If not you'll probably be able to find a PDF version online if you search for the model number.

I learned mostly from the YouTube and there's loads of tutorials there! HowCast has a series of basic sewing tutorials that are very beginner friendly. I still search them sometimes for certain techniques I don't use frequently. coolirpa also has a basic sewing series that's very good. In general just searching "sewing 101" or "sewing machine basics" will give you good results. If you are having specific problems post here again or message me, I'm happy to help! Happy sewing :)

I've found Evelyn Wood 's videos on YouTube really informative and helpful. Also, depending on what you want to sew, some independent pattern companies have really good pattern instructions that are beginner friendly. Some will also have videos to go along with it too. There's lots of sewing stuff on the internet, whether it be basic instructions, free patterns etc etc. Lots of resources!

When I taught myself to sew almost 15 years ago, I leaned very heavily on YouTube. However, sewing is a doing skill. I bought a very easy pattern when it was on super sale (JoAnn does it sometimes) and read it like a book and did my best to sew it. If I didn't understand a step or term, I found a blog or YouTube video to explain it. Each time I tried a new pattern, I understood a little more and my finished pieces were a little more competent. I've found learning to cook to be the exact same way.