Ignore it, it's just angry because you don't have a package file yet. If you can't find the RMC rails themselves, sometimes they'll go a bit off from where you click. You should go into top view, then add them relative to where your coaster is. Generally if your coaster is in a corner you should click in the opposite corner, so you can find them near your coaster, and they don't end up out of the map boundaries.
Mind Bender at SFOG is pretty great
Check out my WIP threadCurrently working on
Thunderbolt, a second generation Schwarzkoph.