As admin user, select 'Layout' in the 'General configuration'
Then click 'Create custom' (if you have not already applied changes to the layout) or 'Edit' (if there are already changes to the default provided by Confluence)
Finally add the above snippet after the rendering of the meta elements
Add HTML meta tags to your Confluence pages. This is for the search engine optimization (SEO) for your website as well as adding semantics for machine reading.