Please reference https://kubernetes.github.io/ingress-nginx/ for information about the NGINX Ingress Controller.
Please reference https://cert-manager.io/ for information about cert manager.
https://github.com/jetstack/cert-manager/releases/download/v1.5.3/cert-manager.yaml
Use kubectl apply -f file.yaml to apply a single file, or kubectl apply -f . to apply all files in the current directory.