Have you tried playing the easy mode of that first scenario? It shall give you a step-to-step guideline on how to set up tourist routes to neighboring cities.

You did skip all dialogue huh?

All that's needed (assuming you want a train line, but the same general logic applies to buses except with the rail replaced by a road)
1. A Station next to the tourist destination (while placing it, connector symbols will appear above the station and destination if they are close enough to count for tourist transit)
2. A rail line that connects this station to the edge of map belonging to whatever city you want the tourists to come from.
3. A passenger train that travels this rail and has scheduled stops to collect and drop of passengers both at the off-map stop and the station you built next to the tourist destination.