Hi @soleron ! Have you checked our samples ?
In the package manager, and the samples table, you can download a unch or samples that should help you to work with some basic use cases like generate a road, move a car along it. Use of the built-in components: SplineAnimate, SplineExtrude and SplineInstantiate. Distance computation between a spline and a 3D point. Use of spline paths to connect different splines together… and else! 
Other than that there is currently no official tutorials on the web to use splines…
You can find some beginning of explanations on the use of splines in the second half of this video from @gabrielw_unity :
https://www.youtube.com/watch?v=BfNNAJ-JhrQ
Hope this help!
Cheers
