Perhaps misleadingly, this is done via the 'Add content' button on a site page. The best thing to do is to navigate to what would be the parent page (e.g. the county or grouping above a neighbouring site) and add it from there. TMA Eds can then approve the submission. Help us out by adding evidence, e.g. links to the site elsewhere online.

This will be made more intuitive in time.

Thanks!
HMCG