To call the CheatSheets select the menuitem Help > CheatSheets.
CheatSheets are a quick help for finding specific markups. Next to the markup-code a little preview of the formatted result is also displayed.
For all of MarkMyWords supported Markup-Languages exists one CheatSheet. Select the desired language by using the popup-menu in the lower-right of the CheatSheets-window.
Furthermore it is possible to view the (semi)official documentation of the selected language by pushing the Visit full documentation-Button.