How would I get that file onto my computer?

I found sem.h, downloaded it, and placed it in the directory (C:\Program Files (x86)\CodeBlocks\MinGW\include). When I ran my program, the compiler said there were lots of problems with sem.h. After doing some research, I found out that I can't just add sem.h as this is just a 'pointer' file which is suppose to point to the actual code behind this function. I am trying to find how to get the actual code on my computer.

Sorry, I am very new to programming in C.