To open Snipping Tool, select the Start button, type snipping tool, and then select it in the search results.
To choose the type of snip you want, select Mode (or, in older versions of Windows, the arrow next to New), and then choose Free-form, Rectangular, Window, or Full-screen Snip.
When making free-form or rectangular snips, use your mouse to select the area that you want to capture.
To take a new screenshot using the same mode you used last, select New.
Use the Save and Copy buttons at the top of the snip to save or copy it to the clipboard.
Keyboard only
To open Snipping Tool, press the Start key, type snipping tool, and then press Enter.
To choose the type of snip you want, press Alt + M keys and then use the arrow keys to choose Free-form, Rectangular, Window, or Full-screen Snip, and then press Enter. (Alt + M is available only with the latest update to Windows 10). When making a rectangular snip, hold down Shift and use the arrow keys to select the area you want to snip.
To take a new screenshot using the same mode you used last, press Alt + N keys.
To save your snip, press Ctrl + S keys. To copy it to the clipboard, press Ctrl + C keys.
Source:
https://support.microsoft.com/en-us/help/4027213/windows-10-open-snipping-tool-and-take-a-screenshot