You can either change the main venue address from the Venue List.
Or, add an alternative address at Checkout.
From the Venue List
Go to Book on the left hand menu, and search the venue list for the unique ID of the venue.
Click to edit the venue and change the details in the correct fields. Click Save.
Adding an alternative address at Checkout
When you go to book for the venue, on the check-out page, you will see the Delivery Address & Contact section
You can view previously added addresses and select them for delivery, or add a new address.
If you need any further details on changing the Contact Details for a venue, see here.