You have to modify the script in the OnData event code. Carriage Return can be added via the escape sequence \r (Carriage Return) or \n (Line Feed). In Javascript string concatenation is done with the + operator.
Menu Configuration - Script Editor - Edit Code: OnData
Change the following code line and add the + "\n" as shown below:
SendKeyStrokes(DATA.replace (/\x00/g, " ") + "\n");
See the FAQ above for a list of common escape sequences.