If you don't have an available Kubernetes cluster, you can create one locally using minikube.
In order to keep the complete demo in the same namespace, first create a namespace in your cluster:
kubectl create namespace kubernetes-demo
After that, apply all changes to the cluster simultaneously. These can also be applied one by one if needed:
kubectl --namespace=kubernetes-demo apply -f app-deployment.yml -f app-service.yml -f app-ingress.yml -f db-deployment.yml -f db-service.yml --record
After running this command, you can go to your dashboard. It should look something like this: