I am setting up my PCs with Norton and have five licenses. Do I use a separate username for each install - or the same one for all five?
There is no username required for an installation of the Norton 360.
If you are physically at each PC for the install, just log into your Norton Account and click on the Download button. Then choose to "install on this device" and follow the directions.
If installing on a device not in your location, just log into your Norton Account, click on Download and follow the instructions to send an email invitation to that device. The user just opens the email and follows the directions to install a pre activated version of your 360. Each email is only good for one installation, so you need to send separate emails for each remote computer.