It is quite simple to insert Emoji and Symbols in Mac OS, you can find the Emoji & Symbols almost in any applications on Mac, select from menu and choose your desired Emoji icons or symbols, then double-click or drag-n-drop it to your application(s).
Do you know the simple method to capture your screen in Mac OS?
Click to System Preferences > Keyboard > Shortcuts > Screen Shots, and you will find the shortcut keys to perform different style of screen captures,
– Save picture directly or copy picture to clipboard with your whole screen
– Save picture directly or copy picture to clipboard with your selected areas
^ means <alt/option> key