Flow run configuration should state the runner
https://docs.prefect.io/api/latest/run_configs.html#kubernetesrun
When you run the flow it should run on a Kubernetes agent
You can tag an agent with labels if you have multiple agents of the same type (i.e. multiple K8s agents)
https://docs.prefect.io/orchestration/agents/overview.html#labels
Labels can then be defined in the flow run config side (KubernetesRun object) to match the agents labels
They state:
A single agent can manage many concurrent flow runs - the only reason to have multiple active agents is if you need to support flow runs on different deployment platforms.
So I am not sure how common it is to do that.