Can't you open your contacts and get a menu with import/export as an option? You don't say what device, what app, or how you are accessing your mail/contacts.
It looks like the Xfinity Connect mobile apps on phones/tablets do not have an option to import/export the contacts/address books. You might have to sign in to your account using a web browser. You can log in at MyXfinity.com and select the Mail icon or go directly to https://connect.xfinity.com/appsuite/ and select AddressBook. There you can click on Address Book and get the Import/Export options.