Overleaf, another free online LaTeX editor, also has agood LaTeX tutorialthat will teach you the basics. They call it an "interactive" tutorial, but it's really just a sequence of slides. That being said, it's a comprehensive introduction to a lot of the commands you might want to try ...
How do I write X bar with the bar over it to denote a vector? I discovered that if I compose a Latex equation here that I can copy it into a Word file. Is this true of all the symbols? Same for sub and super scripts. Is there a software tool that I can use ...