Update README

Author: szarnyasg

paramgenerator/README.md

@@ -2,7 +2,9 @@
 
 The DATAGEN application also runs the parameters generators
 
-For standalone testing, provide the input and output directories as parameters, for example:
+For standalone testing, provide the input and output directories as parameters. The input directory should contain files defining activity a friend list, along with activity and person factors.
+
+For example:
 
 ```bash
 ./generateparamsbi.py ../hadoop ../substitution_parameters