I was going to point you to Blizzard's original tutorials which are a great starting point, but sadly I can't find them... But Deltron did a great video tutorial based off those. You can find the first one here:
Unfortunately, even though I’m a senior software developer for a living, there’s one big flaw with SC2 editor, there is no official documentation.
you'll find some extremely useful documentation here, but it’s 3rd party and is missing some definitions since the many thousands of editable data fields or actor events are documented here as “this doesn’t seem to do anything.”
so that’s kind of how I have to learn things, there’s a ton of trial and error involved here, and you may need to take some of your own notes. Aside from that, this editor is pretty freakin powerful. Just wish the devs made some official documentation about the data fields and actor events/actions, there’s a ton of untapped potential with this editor.