I have a working kubernetes cluster where ingress and letsencrypt is working just fine when I use helm charts. I have a deployment not included in a chart that I want to expose using ingress with TLS. How can I do this with kubectl commands?

EDIT: I can manually create an ingress but I don't have a secret so HTTPS won't work. So my question is probably "How to create a secret with letsencrypt to use on a new ingress for an existing deployment"