You will need to have an account on Xero and add your organization there. In order to use TAP, you will need to provide access to your account on Xero. TAP will then ask you to select the organization you would like to process. Without your Xero account and organization, you will not be able to access and see all the features in TAP.
If you do not have any accounts on Xero, you can sign up with Xero and add your first organization here.
If you are new to Xero, you can learn more about it here https://help.xero.com/int/XeroSignup.