Use kubectl to apply myapp.yaml to a worker or write our own charm for the app?

I am using focal with Juju and k8s and I am a newbie.
I am wondering whether the Juju charm system will allow me to simply kubectl apply -f myapp.yaml or whether we must actually develop our own charm to access the networking of Juju and k8s from our app? I am using the full charmed-kubernetes.