Msce VUE learning sources + Denies access on thumbnail root

Good evening,
I am not new to rendering but I am certainly new to VUE / Microstation. I am looking for sources to learn how to use it. 
I've seen several videos in SIG but I think I need to start from 0, something methodical that analyzes both texturing and lighting.
Hope you can help me! I also take this opportunity to ask for help regarding this error that occurs at the end of the render,
which prevents the thumbnail from being saved, maybe I skipped some preliminary steps?

Thx a lot.