If you're a Fleet Operator, you can view which hubs a Service Provider is auto-assigned to by going to Service Providers > selecting the provider > and checking their Ticket Settings — but only the Service Provider can change these settings. Get in touch with them if they need to be changed.
If you're a Service Provider, you can auto-assign yourself to client hubs by:
Go to the Client page → click Ticket Settings → select the hubs where you want to be auto-assigned > Save.
You can manage auto-assign settings for Maintenance Partner in the same way.