How do I change what computer I have selected

I downloaded whatpulse on my laptop and had to chose my old computer as the one I was using, but now that I have gone to MyWhatPulse and made a new “Computer” how do i change to that one?

Pulse if you haven’t, press Logout in the Account tab, then log in with your username and password again, but select the other computer in the box which asks you to select your computer.

Difficult stuff…