Update SECRET README.md

src/usecases/SECRET/README.md

@@ -2,3 +2,12 @@ The SECRET Model - Applied to PipeFabric
 ========================================
 
 See [project website](https://www.systems.ethz.ch/research/SECRET/) for details.
+
+## Usage (after building) ##
+```
+./secret [winType expNum]
+```
+
+- *winType* - the window type, either "time" or "tuple" (without quotes)
+- *expNum* - the experiment number, 1-6 for time-based windows and 1-5 for tuple-based windows
+- without additional arguments all experiments are sequentially executed
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