If you want to release your application as open-source software, you would want to create an additional package for users who would want to look into how your application has been made or recompile the source code for themselves.

The other case might be that you are working in a team and have to exchange source files. In this case, it is strongly recommended to use version control software though.

Make sure you just have plain text files, such as C/C++ headers (*.h), C++ source files (*.cpp), project files such as *.sln for Visual Studio or *.cbproj for CodeBlocks. Just use a packager of your choice and create a compressed package of all files necessary. In the Linux world, source code packages usually have a *.tar.gz file extension.

If you release your application as open-source software, you should also include a full text version of the license of your liking in your package file. If Irrlicht code is in the package, it also requires the zlib license to be included, and probably also all other license files that are contained in the Irrlicht SDK.