To update a member's contact details on GovernorHub, click on the arrow to the right-hand side of their name in the members list. This will reveal a drop-down menu. One of the options is View Name's full profile. Click this button.
This takes you to a member's profile page where you can update their basic details, contact information, declarations of interest and training records.
Note: if a governor is a member of multiple boards, this will update their details across all their schools.