Welcome to AM!
Yes, it is better to keep your routes down to 1 freq which means it's a return flight, i.e creating a route from your base to an airport on freq 1 means that it's a return so the aircraft returns to your base. So when you create the next route with the same aircraft, it will be from your hub and not from the destination airport.
So this is what you do in relation to your post: Create one route on freq 1 from Basel - London and then Basel - Paris and then obviously add more routes to fill up the flying time of the aircraft. (Assuming Basel is your base??)
If you want the aircraft to serve different airports before returning to your base, you will need to have a base at each airport where the flight will take off, i.e. London - Paris and then Paris - Frankfurt for instance, means you will have to have a base at London and a base at Paris to launch the flight from Paris or be part of an alliance who has got a base at Paris, which means you can launch an alliance flight. That is why when you create a route on freq 1, the aircraft returns to it's starting point which means you can create another few routes from your base again to different airports.
Does that make sense?
