There are many ways of finding and writing GPS co-ordinates. The easiest way I know is using GeoSetter.
GeoSetter is free software compatible with Windows XP and higher.
GeoSetter is integrated with Google Maps. So type your known address into the Search box, click Search and it will return the co-ordinates as well as putting a pin on the map.
You can zoom the map and move the pin to the exact location and the co-ordinates will also adjust.
Use this button above the map to apply the co-ordinates to the select image(s).
You can also use the Add/Edit option to add this location to your Favorites list. In the future you can re-use this template by clicking the arrow for the drop-down list in the Map or Edit view.
Just fill in the information and click OK.
The Location Favorites can be accessed under File/Location Favorites. They’re listed automatically by Country/State/City.
The Location Favorites can (should) also be backed up using the Backup Settings option. This resulting zip file will include any templates you’ve created.
If you click on a thumbnail where you’ve added GPS co-ordinates and Images/Edit Data, you’ll see this screen where the GPS is written in two formats; decimal and sexagesimal. Altitude can be retrieved from the web with a click of a button for most locations.
The GPS co-ordinates can be set to show below the thumbnails.
Under View/Image Files/Adjust Columns and Captions, you can choose what fields you want showing in Thumbnail View and in which order.
As well as making it easy to write GPS and other location information, GeoSetter can also be used to add metadata like keywords, captions, source, copyright, etc. This is an excellent video that shows both.