I couldn't get to know how to assign the input and output pins. I tried assigning the ports with the lable as In and Out, later i couldn't use it to plot the results.
You have to use place global label which is present in right hand side toolbar of schematic editor window and then assign as input and output. After this generate netlist and you check the output.
1. You have to generate spice netlist as Default format after assigning the in/out labels.
2. For half adder, close the esim then again run the example any try.