This is my first time posting so I hope it gets through. In Gnome 3 based distributions (Ubuntu/Debian/Fedora etc) you can switch workspaces by going to the Activities screen and using the scroll wheel on the mouse or by clicking on the right pane. Alternatively you can press Super+Page Up (or Super+Page Down) on the keyboard to cycle through your workspaces. If you are using a PC the 'super' key is the Windows key.