Update instruction for plain command service

systemd-service-files/plain_command.service

@@ -1,8 +1,12 @@
-# to install the file, place completed file in /etc/systemd/user/
-# you can start it with:
+# to install the file, place completed file in /etc/systemd/system/
+# reload the daemon to load your new service file:
+# `systemctl daemon-reload`
+# you can now start it with:
 # `systemctl start FILE_NAME_WITHOUT_DOT_SERVICE`
 # or enable it at boot with:
 # `systemctl enable FILE_NAME_WITHOUT_DOT_SERVICE`
+# or do both with:
+# `systemctl enable --now FILE_NAME_WITHOUT_DOT_SERVICE`
 
 [Unit]
 # basic description of service; replace with legit description