How to create a river spline blueprint?

Hi guys, I just wanted to know how to create a river spline blueprint from scratch. I’m new to using unreal engine 4 and from all the tutorials i’ve seen so far, all downloaded the Nature Procedural Pack which cost around $80… I was thinking that maybe instead of buying this pack, there would be someone out there that is brimming with knowledge on blueprint scripting and can help me in creating a river blueprint from scratch. Thank you