With Nova ADC you describe a service, not a server. Once you are ready to deploy that service to one or more servers you are "Deploying" in Nova terminology. This attaches that ADC configuration to Nodes.
Once you have created an ADC you can deploy it. Alternatively, you can add or modify the attached Nodes to an ADC by selecting Deploy and Attach in the ADC actions menu.
This will link the ADC configuration to one or more Nodes, ensuring they are always running your ADC template, and all the requirements of it (WAF, Geofencing, Logging, etc).
To attach an ADC you must have at least one online Node that is ready to receive the configuration. This Node will then function as the ADC, and you can send traffic directly to the Node (not via Nova).
You can attach multiple ADCs to a single Node if you wish, however, you must ensure there is no IP:port clash between them. For example, you cannot deploy two ADCs that both listen on 0.0.0.0:80 as they will clash.
Should you want to have multiple websites for example, deploy one ADC with multiple Backends enabled instead.