Welcome to Grasshopper for rhino, u can go directly into grasshopper intro to understand how the components and everything works. if you are using Railclone before and want to array in GH, here i made some simple explanation:
A. Segment in RC is “Brep, or Surface” in GH. assign by right click and then pick geometry.
B. L1S in RC is “Move + series” component in GH.
C. RC is using Spline direction, in GH it is “Vector direction”. u can make vector along X,Y,Z or any other direction u like
D. RC has properties built in inside L1S, in Rhino, you provide the GH component information by feeding it from numbers component / equivalent.
this is a simple explanation to get u started.