First, you will want to open your Snipping Tool.
Once you have opened the Snipping Tool, you will want to "Capture a Snip". You can proceed to take a screenshot by following the instructions pictured below.
Pro Tip: the "Mode" tab will allow you to select a type of screenshot (ex: a "Rectangular Snip" is great for screenshots of sections within a window browser whereas a "Full-screen Snip" helps if you need a screenshot view of your desktop screen).
First, press and hold these three keys together: Shift, Command, and 4.
You will then want to drag the crosshair ⌖ to select the area of the screen to capture. To move the selection, press and hold Space bar while dragging. To cancel taking the screenshot, press the Esc (Escape) key.
To take the screenshot, release your mouse or trackpad button. If you see a thumbnail in the corner of the screen, click it to edit the screenshot or wait for the screenshot to save to your desktop.
By default, screenshots save to your desktop with the name, "Screen Shot [date] at [time].png".