As said by Kadeschui
You are going to have some issues unless you pass the Revit model through another application like 3DS Max to re-scale the geometry and create your UV's, beforehand.
Revit will not create UV's for your models and in my experience, your geometry is going to be pretty messy (very high poly and un-optimized geometry, inverted face normals, etc.).
If you just want a quick walk-through of your Revit model, you can make some minor tweaks in 3DS Max and have a decent, untextured model to view in Unreal. For anything more - even close to an ArchViz quality scene (let alone photo-real) - you're better off re-modelling everything in another program.
This is why you don't see architects pulling their revit models directly for renders; instead they re-model/hire another company for visualizations.
Some tips:
1. Try to break up larger models. If you have a house with 10 rooms, don't import them all at once as one model. Break it up into seperate rooms and import 10 files, then just drop them into the scene (they should automatically be arranged if you click+drag them in all at once)
2. In addition to above, you don't want to separate any wall or floor that is visually contiguous. Walls that meet at corners are fine but separating a continuous wall and joining them together causes seaming since UE4 renders each geometry on a different thread during building. You can see what I mean here:
3. Be sure to convert them to standard materials. Also, take a look at tom shannon's maxscript, it's a huge time saver. http://www.tomshannon3d.com/2014/09/tstoolsv11.html
Hope this helps
Best Regards