Hi, good luck with the cluster! You are talking about deploying applications to Kubernetes running on your cluster?
The applications are containers - e.g. like a docker image. You can just fetch a docker image and ‘install’ it by telling kubernetes what to run, or you can use another system to make creatinga and managing the container easier. Some people use things like Helm (you can just microk8s enable helm) but for installing and managing the applications you should check out Juju. Once set up you can then just deploy the apps you want and link them together.