Referenced Models not showing up

I am following this video below on how to create a complex terrain model and my referenced models are not showing up under OpenRoads Model. 

https://communities.bentley.com/products/road___site_design/w/road_and_site_design__wiki/35094/video-create-complex-terrain-model

I started with a 3d seed file and then I attached the existing terrain and the corridor files as 3d model references and they aren't showing up in "Referenced models" under OpenRoads Model. Any suggestions? 

Thanks, 

Megan