The desktop tracker will be running in the background, so there is no program that is going to be opened. You will see the icon with the logo on the menu bar in the top right-hand corner on an Apple computer, or in the tray at the bottom right corner of a Windows computer.
On a Windows computer, there may be too many icons in the tray to see them all. You will have to click the upward arrow in the tray in order to see them all.
If you still cannot see them, restart the computer. If that doesn't fix the issue, remove the software and reinstall it using the link that was sent with the invitation email.
If that still does not resolve the problem, contact YouGov with the operating system, error message and browser version for assistance.