the TRIAL version is not limited in those functionalities.
since the CityEngine project is set up in project folder structure, you need to first place your files you want to work with in the CityEngine project. things you want to use must be placed in those folders to work with them, thus we named those folders as a default.
directly linking files from ArcGIS is not yet possible, thus you need to work with e.g. picture files or 3d assets.
please note also that it's best to work with picture files smaller around 4096x4096 pixels due to the fact that CityEngine handles textures in memory and not as a 'service' as e.g. ArcMap which enables unlimited data (e.g. tiled 10 GB GeoTifs). Thus, if you want to visualize large datasets, you'll need to use the CityEngine as content creation tool and bring the final buildings to e.g. ArcScene, which were created based on a 'down-resed' terrain model.
DEMs, TINs and GRID-based terrains are not yet supported, thus you need to work with raster-based terrains such as 32 bit tif files.
Here's some resources :
--> check Gallery !