PREREQUISITES: Make sure you signed up with Royal Mail. For this purpose:
Create your free API account here.
Enter a valid email address when registering an account with Royal Mail, as Royal Mail will send you a verification link to activate your account after the registration.
Register your application in the "My Apps" section of your Royal Mail account as described here.
When you register, your application is assigned a unique client ID and client secret. You'll need these data to configure the Royal Mail add-on in your X-Cart-based store.
Subscribe to a Royal Mail API in your Royal Mail account as it needs approval by Royal Mail; this usually takes less than a week.
To configure the Royal Mail add-on, open the add-on settings page (Store Setup > Royal Mail Service) :
Here you will need to specify the following information:
Client ID: Your Royal Mail client ID.
Client Secret: Your Royal Mail password.
API Username: Your Royal Mail API username.
API Password: Your Royal Mail API password.
Application ID: Your Royal Mail application ID
Save API request/response to log file: Turn the toggle on to log the Royal Mail server incoming and outcoming requests. The logs are saved to RM.log files in the /var/log/ folder.
Be sure to Submit the configuration settings to make them active.
Then you will need to proceed to the Royal Mail Services tab (Store setup > Royal Mail Service > Royal Mail Services) to set up the service relations:
To add a new relation, click the Add relation button and select the values from the dropdown fields in the new relation's line in series:
Save the changes when ready.
Royal Mail Services does not have an API facilitating online shipping rates calculation. Hence a merchant cannot use the Royal Mail Services add-on for calculating online shipping rates at checkout, but only for shipping orders via the Royal Mail Services.
Please ensure you have offline shipping rates configured in conjunction with the Royal Mail rates and relations you set up to offer shipping calculations at checkout to your customers.