I’m actually working on same project, there are two ways to deal with,
1. First you can read the matlab path directly from your file ex: C:\Users\XXXX\Desktop\testnew.m
2. Second, you can write your script on matlab and copy and past it inside of Optisystem (matlab component); be careful to better defined your input signal type, i mean (Optical or Electrical).
See the file below for your reference.
Get Started
Cheers !!!!!!!!!!!!!1!1