added usage description

Author: mpibpc-mroose

README.md

@@ -11,3 +11,23 @@ So I decided to implement it's functionality in Python.
 
 There is no warranty for a 100% compatibilty to the old plugin, but
 requests for adaptions and error reports are always welcome.
+
+# How to use it
+
+1. copy `check_pcmeasure.py' to your Nagios plugin folder
+1. define a nagios command:
+```
+define command{
+    command_name       check_messpc
+    command_line       $USER1$/check_pcmeasure.py -H $HOSTADDRESS$ -w $ARG1$ -c $ARG2$ -S $ARG3
+}
+```
+1. define a service
+```
+define service{
+    use                     generic-service
+    host_name               messpc.example.com
+    service_description     temperature sensor
+    check_command           check_messpc!28!30!com1.1
+}
+```