The OEE is an outcome of the simulation run. If you drop a SingleProc onto a Chart object, you will see the development of the OEE statistics. The resulting OEE follows from the settings of the SingleProc itself and its interactions with its environment.
You could also compare the ouput from the line with the target output, this will more or less be the OEE value for the line.
Simulated value = 75,6 pieces per hour
Target value = 100 pieces per hour
OEE for the line = 75,6/100 = 75,6% OEE