add a missing detail

docs/MANUAL.md

@@ -157,6 +157,8 @@ chown oragono:oragono /home/oragono/tls.*
 systemctl reload oragono.service
 ````
 
+Executing this script manually will install the certificates for the first time and perform a rehash, enabling them.
+
 You can also change the ownership of the files under `/etc/letsencrypt` so that the oragono user can read them, as described in the [UnrealIRCd documentation](https://www.unrealircd.org/docs/Setting_up_certbot_for_use_with_UnrealIRCd#Tweaking_permissions_on_the_key_file), but this is not recommended if you plan to use the certificate for services other than oragono.
 
 On a non-systemd system, oragono can be configured to log to a file and used [logrotate(8)](https://linux.die.net/man/8/logrotate), since it will reopen its log files (as well as rehashing the config file) upon receiving a SIGHUP.