1. Edit domain and find out "Add Let's Encrypt" button.
It will create one SSL certyficate for domain itself and all aliases.
2. Follow all steps 1-4.
When you finish, click "Activate Certificate" button.
3. Your SSL certificate is ready to use.
Make sure the domain is listen at 443 port.
4. Enjoy your domain via HTTPS.
TinyCP will auto renew certificate for you.