Cannot upload images

Try changing the permissions on the wp-content directory to 766. If you still have problems, try 767, 775 or 777. Once your uploads are working, change the permissions on wp-content back to 755 again and check that everything still works OK.
https://codex.www.ads-software.com/Changing_File_Permissions

Thanks, I right clicked on the wp-content folder and selected properties but cannot find out how to enter the 766 you refer to.

Apparently the problem is because WordPress is sitting on a Windows platform with my host, rather than a Linux platform.