While I'm not in a postiton to test nontheless I doubt that VMware Workstation is Touchscreen aware and probably is not able to pass the swipes into the Windows 8 Guest, so you'll need to use either the Keyboard or Mouse.
Keyboard Shortcut: WinKey+C
Mouse: Move your mouse cursor to the top or bottom right corner of the screen, then move the cursor up or down towards the transparent charm icons that appear in the middle of your screen.