To install C or C++ compiler in your computer, download it first from any of these web sites.
Then, do the following if you have a not working or not needed C or C++ compiler in your computer.
1) Uninstall the not working or not needed C or C++ compiler.
2) The C or C++ compiler you just downloaded will be in a .zip format. So, extract it.
3) Now, open the setup.exe to start installing C or C++ in your computer.
4) Follow the steps given by setup.exe to install C or C++ compiler in your computer.
In case you are installing a C or C++ compiler for the first time, you can follow the last three steps mentioned above.
Hope this answer helps.