The following article demonstrates how to add enabled the Slidey Bar embedded app in the new section supporting (OS2) themes in Shopify.
Important Note: To display the Slidey Bar and its content requires both the Embed enabled and a Slidey Bar section content block installed. Click here on how to add a content block
Open your Theme Customisation menu and on the left side click on the 'App embeds' option
Select the Slidey Bar app embed and toggle enable and click Save