All key combinations are gathered in a single reference window inside the program (the Help menu), and here’s the full summary with explanations. The most common ones are worth memorizing: in a show, a key is faster than the mouse.
“?” icons are placed throughout the interface — hover over one and an explanation of the element appears in plain language. If you forget what a button does, look for the “?” next to it.
Help → App tour will walk you through the main parts of the interface again — handy to return to after your first look around.
Help → Documentation (the F1 key) opens this manual.