The guide I am writing here is the same for both Cables Galore and Clark Cable (Transport 5,000 passengers).
Build up your city naturally but don't place any public transport yet. When you unlock cables cars, use them as your only public transport route.
When you place them, make sure that the route between two places is made shorter by use of cable cars, since your cims will use whatever route is shortest.
One way of using this is to create a route from an estate/part of your city that is at sea level to another area that is very high up. This will encourage the use of this (especially if you have made winding roads to that destination).
You could also place this across two area of tour city separated by your highway/motorway.
This public transport route seems a bit over the top and not necessary in your city so you might find that it becomes underutilised. This achievement will unlock but it will take time.