Impossible to use a shared File

My Cloud OS 3 Personal & Network Attached Storage My Cloud
1

Hi everybody,
A friend recently bought a mycloud. He invited me to a shared file.
I can access to it using my browser but I don’t have a local file where the documents are synchronised (like dropbox or box).
Where can I chose to synchronise the shared file?

Thanks for your help !

2

If your friend invited you then it is his file. What kind of invitation did he/she give you? See image below.

3

It was a private sharing.
Should he choose Collaboration ?