Scarcity Maker plugin provides some shortcode functionality. There are two ways to use shortcode in post.
1) Admin Menu on the left hand side.Select "Scracity Maker".
On that Page you can list of Scarcity.From that list select any one shortcode.
For example your shortcode is [scarcity id = 14] - Display counter which have id 14.
2) You will see a Scarcity Maker shortcode icon within the WordPress editor, just as shown in the image below :
Click on the icon and a new window with the custom settings will pop up. Within these settings you have the ability to select scarcity from list of scarcities.
After insert short-code it will look something like the one shown in the image below on frontend.