Go to: Account > Settings > Email settings
Scroll down for the Broadcast campaigns settings:
- Your tracking parameter
- The parameter value
See the list of default tracking parameters for reference.
You can also select a user attribute from the Insert personalisation drop-down list.
This will populate the required merge tag, allowing you to track attribution specific to the contact who clicks through to those fields.
You can use Insert personalisation, or you can use any merge tags to include data here.
Select Add to add further parameters.
Click Save to preserve your changes.