Hello and welcome to the Seamly2D forum, @LizQ
When I found Seamly in 2017, I suddenly discovered that I also need to learn HOW to create a pattern. I settled on Winifred Aldrich’s books because she gives something of almost everything you would like to make in very easy, step-by-step instructions that are easily translated into Seamly2D.
Later that year, I put together a PDF tutorial for an easy fitting blouse pattern that you can find in this chat: New member, any spanish speakers? - #9 by Grace
I have since worked my way through various books and have figured out a lot of other things to do with pattern making, but I often go back to Aldrich’s books, so I think, for personal use, this is a very good place to start. 