Hello Granny Debs, welcome to The Modern Antiquarian!
To add a new site, you find the main page for the region you wish to add a site to, e.g. for Alentejo:

https://www.themodernantiquarian.com/site/13470/alentejo

From here, click the 'Add content' button and then 'Add a site'.

Once submitted, the site will then sit for approval by TMA Eds. Please provide evidence for the site existing with your submission, as that helps achieve much speedier approval.

Thanks and best wishes,
TMA Ed.