The order of taking a screenshot depends on which device or platform you want to take it from. Most often, on the keyboard or device case, you already have shortcuts that allow you to make a screen.
Instructions for popular device types: computer, tablet и telephone.
Instructions for popular platforms: Windows, Mac OS, Andoid and iOS.
Among other things, there are simple universal programs for taking screenshots from third-party developers: Joxi (joxi.ru) and Lightshot (app.prntscr.com/ru/).