It's pretty straightforward - you sit in one room with a PC, set of headphones and a chart - the examiner sits in another room and plays the role of various ground stations and other aircraft.
You 'fly' a route on the PC using the mouse to control your aircraft speed and direction following the proscribed route, making the appropriate r/t calls. Expect stuff such as zone transits, MATZ penetrations, circuit calls, a MAYDAY, and perhaps a bit of direction finding.
The hardest bit was controlling the PC!
If your instructor reckons you're ready, then you shouldn't have a problem.