There's your problem. Compiling refers to the process of converting your modified C++ source files into a new DLL for the game. Simply modifying the source code doesn't have any effect on the game.
The adding a civ guide doesn't really specify this because it is an advanced procedure that basically assumes you're sufficiently familiar with programming (also because it's just a copy of a post in this thread which runs under the general assumption that you generally know about this stuff). I've updated it to make this clearer.
There are a couple of guides for setting up your SDK to compile the DLL, I think asaf's guide is preferable for beginners.
The adding a civ guide doesn't really specify this because it is an advanced procedure that basically assumes you're sufficiently familiar with programming (also because it's just a copy of a post in this thread which runs under the general assumption that you generally know about this stuff). I've updated it to make this clearer.
There are a couple of guides for setting up your SDK to compile the DLL, I think asaf's guide is preferable for beginners.