See the link at the top this page to the original post that includes more videos.
Most of the time you probably mostly want to use a Map Import constructed drawing file as separate XREFs in your project.
Ron sort of hanky waves over the actual importance of a well-built import template file in this process.
Note that the Civil 3D 2019.1 update includes improved LandXML Import and Export Settings options for Feature Lines amoung other things.
Of course, LandXML import/export is not the same thing as Map import/export at all.