Good morning Jane
The computers must have some way of getting onto the internet, be it with a network, or their own internet connection.
If they can all get on the internet, then just set it up as you did on your own computer, but rather than signing up for a new account, just say you've got an existing account, and enter the email address you used to sign up with
If you have the computers on a network, then you may wish to have a look at
SetiQueue. This works as a central location for all your networked computers to collect Work Units from, and it also gives you many stats on how many WUs/day each machine is doing, and the time it took for each WU to complete.
It may seem a little daunting to set up at first, but it's quite simple, and just ask if you have any problems
Garry