Which platform feature should a beginner learn first on MT4 or MT5?

MetaTrader has hundreds of features, but beginners only need a handful: placing a market order, attaching a stop-loss and take-profit, modifying an open order, and reading the terminal window.

Experienced members: if you could teach a beginner just five things in MetaTrader, what would they be? And beginners: which button or window still confuses you?

One answer per reply keeps it readable. The platform comparison sets the context.