Property:Has WGS84 coordinates
Coordinates are assumed to use the WGS84 system, which is the system for geographic coordinates used by Google Maps, Geonames, Open Street Map, Wikidata and many others but is different from the Ordnance Survey National Grid. ETRS89 geodetic coordinates are near enough that they can be entered here but the software will treat them as WGS84 afterwards.
Latitude comes first, and longitude second, separated by a comma. You can enter the values as decimal degrees or as degrees, minutes and seconds. They are automatically displayed on the page as degrees, minutes and seconds.