The address details are inside a text widget (you can tell that from looking at the various elements that it is in on the source code for the page).
To modify this, you will go into your admin area, then go to ‘Appearance’ -> ‘Widgets’. This will show you the list of sidebars on the right-hand side. Choose the sidebar that you are using, and edit the text widget in there and it will change.
Thank you very much. I found it. I have made the changes a little while ago, although they are not showing up on the web site. Maybe it just takes a while.