Scott Christian
Hero
The 2014 DM's guide (the intro and first chapter), Matt Mercer and Satine Phoenix's videos on GM tips, and actual in-person playtime as a player with a good DM. That is what I would start with.
Note: If they are still too young to read and understand the DM's Guide, read it with or to them.
Note: If they are still too young to read and understand the DM's Guide, read it with or to them.