extend the README with a configuration section

This section should give a short introduction on how to configure the
system.
There should be a frontend to do the same thing later.

README.md

@@ -40,3 +40,50 @@ It is responsible to cleanup the history and generate the configuration.
 
 The configuration is generated into `active_checks` when an entry in `nodes`,
 `command` or `checks` was changed (detected through the updated column).
+
+configuration
+-------------
+
+To get the system working, first install the database. After that, create an
+alarm mapping:
+
+```
+insert into mappings(name, description) values ('default', 'The default mapping');
+insert into mapping_level values (1, 0, 0, 'okay', 'green');
+insert into mapping_level values (1, 1, 1, 'okay', 'orange');
+insert into mapping_level values (1, 2, 2, 'okay', 'red');
+insert into mapping_level values (1, 3, 3, 'okay', 'gray');
+```
+
+Next is to create a notifier. This feature doesn't work 100% yet and needs some
+work and may look different later:
+
+```
+insert into notifier(name) values ('default');
+```
+
+After that create a check command:
+
+```
+insert into commands(name, command, message) values ('ping', 'ping -n -c 1 {{ .ip }}', 'Ping a target');
+```
+
+This command can contain variables that are set in the check. It will be executed by moncheck and the result stored.
+
+After that, create a node which will get the checks attached:
+
+```
+insert into nodes(name, message) values ('localhost', 'My localhost is my castle');
+```
+
+With that prepared, create the first check:
+
+```
+insert into checks(node_id, command_id, notifier_id, message, options)
+values (1, 1, 1, 'This is my localhost ping check!', '{"ip": "127.0.0.1"}');
+```
+
+Now start the daemons moncheck, monfront and monwork.
+
+monwork will transform the configured check into an active check, while moncheck
+will run the actual checks. Through monfront one can view the current status.