How to include an MKT area to a user's role?

Hello experts

In Customer Trips, a user can only see those that belong to their MKT area.

I've been through the documentation and it says: "To include interactions in your customer journeys that don't have a marketing area assigned, make sure your user role is also assigned to a blank marketing area. A blank marketing area is represented by a space enclosed in single quotes ('').

For more information, see Contacts and Interactions "

How can I assign a blank MKT area to a user's role?

Best regards

Elio C