How can I add a new address to the Service Centre List

I believe you are asking about your form 52801948547464, named "Our Service Centre".

I see that this form does not have a Submit button, and therefore cannot collect any form responses and cannot act as an actual form. It is being used solely for displaying information to people who navigate to its URL:

https://form.jotform.me/form/52801948547464

Your form is using Text fields to display the information. You can simply add another Text field to your form, and enter the new address into the newly created Text field:

If you want to conditionally display the newly created Text field based on what a customer selects in the "Select your City" field, you can use the show/hide conditions:

https://www.jotform.com/help/57-Smart-Forms-Using-Conditional-Logic