On OS X Mavericks: Find the emoji keyboard using “Cmd + Ctrl + Space”.
On Windows 10: Look for the keyboard icon in the Windows taskbar in the lower-right corner to bring up the Windows Touch Keyboard. Then click on the face to the left of the space bar and to the right of the Ctrl button in the Windows Touch Keyboard.
On Windows 8: You’ll want to add a keyboard button to your Taskbar by right-clicking anywhere on it and hovering over Toolbars. Next select, Touch Keyboard in the menu. Now you should have a Touch Keyboard button in your Taskbar. Just click on that button and you can access emoji on Windows 8.