I have a c++ code which upon build gives me .so file. I want to use the methods from that .so file into my robot framework. Any suggestions please.
You can create your own test library that would support calling functions of your so within Robot framework. Here is the official guidelines for creating test libraries. As they recommend in the guidelines, in order to integrate the code of shared libraries to your tests you should use ctypes python library in your robot framework test library code.