Simulink Masking and S-functions ..

Hello , I am new to S-functions and Masking and Unfortunately , haven't found any good examples in Documentation to learn & understand it.

Let me get straight to the point. I have a working model in which a user-defined block "myFOO " is used , which depends on myFOO.c and myFOO.mexw64 .. I ummasked the block and found the S-fucntion name ''myFOO.c'' has been written in the block..

My Question is how Can i use myFunc.c and myFunc.mexw64 to get a User defined block myFunc in Simulink so that I can know the functionality of the myFunc.....

I an quite new to this User defined blocks , So apologies if the question seems wrong.. Please do let me know if you have any questions..