What's best to do is go the home page, and click on the right part of the little map on the right. Most things are in counties, so just pick the right county and then click on the 'add' bar on the right. Scroll down to 'add site'. Then your site will go in the right county, and you can put in the grid reference for it, and pick the site type and everything.
Or just type the county name into the 'Quick search' box, and then add the site.
hope that makes a little sense?
(but your latest site is still medieval? in which case you'll have to get its coat I'm afraid).