You don’t need the customizer to do that (and it doesn’t do that anyway).
Please check the documentation for the main (free) plugin here:
https://stephensherrardplugins.com/docs/pta-volunteer-sign-up-sheets-documentation/
Scroll down to the part about shortcodes and all the available shortcode arguments. If you include the ID for a specific sheet in the arguments for the shortcode on a page, then it will only show that sheet on the page, instead of a list of all available sheets.