SSL: Use own certificate

docs/firststeps-ssl.md

@@ -23,6 +23,12 @@ ADDITIONAL_SAN="cert1.example.org cert1.example.com cert2.example.org cert3.exam
 
 Each name will be validated against its IPv4 address.
 
+## Use own certificates
+
+To use your own certificates, just save the combined certificate (containing the certificate and intermediate CA/CA if any) to `data/assets/ssl/cert.pem` and the corresponding key to `data/assets/ssl/key.pem`.
+
+Restart the mailcow stack by running `docker-compose down && docker-compose up -d`.
+
 ## Check your configuration
 
 Run `docker-compose logs acme-mailcow` to find out why a validation fails.