Unmanaged Server

I am trying to install avast server edition on a server taht will be in our DMZ. We have licensing for 25 servers and i have a license for this server. I want to manually install the software on this server. HOw do i install a licesnse for this server without connecting it to our network. I want it to be able to get its updates from the internet. So i assume this has to be licensed.

Here’s a link on how to install the license.

https://support.avast.com/index.php?_m=knowledgebase&_a=viewarticle&kbarticleid=349&nav=0,1,23,24