Hi Don,
It depends on what actually you're looking for and what you mean by creating.
Do you mean creating them in game, or actual content creation? I'm assuming since it is in this area here, that you are trying to figure out how to lay splines.
Splines refer to a lot of things... Fences, roads, buildings, cars, sidewalks, tracks, grasses, trees and even entire farms can be laid with splines. If this is what you're talking about, then we can help further.
Oops! Sorry. I should have looked harder for the correct forum. I'm interested in creating some simple splines. I'll see if I can get some help over on the Content Creation forum.