On the contact list you want, click the ✏️ Edit button on the right
Change the contact list options however you want:
Contact list name
Email prefix - This prefix shows up in the subject lines of emails so your contacts can spot emails from your organization more easily. It's a good idea to choose a short prefix.
Sender name - This is the text used to identify your organization in sent emails. The name can be up to 30 characters long.
Language
Welcome message - This message gets shown in emails that go out to new recipients when they get added.
Enable/disable double opt-in - Recipients will be asked to confirm they want to get email notifications
Save changes