First, whenever a downloaded track comes with 3DS-pbjects all these objects-files MUST be moved to the '/objects'-subfolder of your NL installation directory or else NL wont 'see' them.
Second, whenever you want to place an 3DS-object within one of your tracks, be sure that this object is within the abovementioned '/objects' folder also, along with any corresponding object textures.
Third, in the NL editor choose menu [Scenery]/[Choose Scene Object..] and select the filename of the 'thingy' you want to place then.
Fourth, see NL-help for scaling and rotating an object within the NL editor (there are different colored handles attached to the object to manipulate it)
hope this helps...
redunzelizer