Get the newest version of the offline viewer here :
Some docs about this are in the manual :
F1 CE Help > Manual > Exporting Models > CityEngine Web Scenes > 3 Publish to ArcGIS online > Scroll down to : 'Upload to custom server'
More docs here :
It'd be great if I was able to send a CE scene to someone on another computer who doesn't have CE but has something like the offline viewer so that they can look at a model and take snapshots from the angles they want. Is this possible? Just thinking then I could just send them the .3ws file rather than having to go through the internet etc.