@hagglawphx Thank you for using and supporting our product! We checked your account information, and the product you're using is Antivirus+ Security which is only for 1 PC.
Unfortunately there is currently no way to add a single seat/device on your 1 PC license. If you'd like to protect other computer, you can: - Purchase a separate Antivirus+ Security license now - When you renew your Antivirus+ Security next year, upgrade to Internet Security or Maximum Security or Premium Security to protect more devices using 1 license
For a side-by-side comparison on the different editions, please see: Trend Micro Security 10 Software - see "Compare the key benefits of Trend Micro Security software" section.
Thanks and please let us know if you have more questions!