You should able to register the software from any computer with internet access, for example,

a home computer with internet access.

All you need to do is install software to those PC as normal, and jot down their response code from Software Register page in the software.

Go to this website and get the license key online from any computer with internet connection:

https://www.myusbonly.com/usbregistration/registration.php

Enter each key into those installed PCs. Note that you should paste correct license key which generate from each response code.