Welcome, David! 
If you’re up for some reading, the Introduction manual explains the core concepts and philosophy behind Defold—it’s also a gateway read into heavier manuals. Furthermore, the tutorials are a great way to delve into the engine and learn by doing.
There are also some great community resources as well—gamefromscratch.com, for example, has an always-expanding selection of text and video tutorials.
And if you’re new to Lua, here’s a big list of Lua resources, compiled by @Pkeod.
There’s of course a lot more out there—but this might be enough to get started.