I haven't seen koolplot anywhere in my Code Blocks but it need not matter. The error often says that a header or a library has not been found. Therefore, install koolpkot, open your project, set path to koolplot headers in Build Options -> Search Directories and set path to koolplot libraries in Build Options -> Linker Settings. Compile. You should pass. You can also create a custom "koolplot project" with these paths preset. Later on, you can write koolplot projects without setting the paths again.