To edit the location to a photo , open the Info panel and type the name of a place or an address into the location field of the Info panel, or, if you know the exact latitude and longitude, type the latitude and longitude in degrees into this field, see: https://help.apple.com/photos/mac/1.2/?lang=en#/phta4e5a733f
Location: Enter a location in the Location field. As you type, Photos suggests locations that you can choose. To change a location, you can search for a different location or change the location by dragging a pin on the map. To remove location information that you assigned manually to a photo, delete it or choose Image > Location, then choose Remove Location or Revert to Original Location. You can’t assign a location if your computer is not connected to the Internet.
But the photos do not need to have locations assigned to add places markers on a map page of a photo book. See the section "Add, remove, and rename place markers on a map" on this Help page: https://help.apple.com/photos/mac/1.2/?lang=en#/pht245fde94