The Users screen does not work and so there does not appear to be any way to specify which Unattended Computers that users should have access to. I previously reported this via a chat session a while back, but it has not been resolved and no ticket was assigned to me, so I want to raise this issue again here for others to see.
Here's a screenshot of the page showing that Zoho Assist has some sort of server side error preventing this page from working: