How to have a sub project within project and decide which one to run?

Hey

I'm fairly new to this so I'm not sure if this is cmake question or cLion as cLion does some management of projects. In any case

I have

projectFolder
    testFolder
        testProjectAFolder
            CMakeList.txt
            main.cpp
        testProjectBFlder
            CMakeList.txt
            main.cpp
    libraryFolder
         liba.h
         liba.cpp

    cmake-build-debug
    CMakeList.txt
    main.cpp

How can I configure cLIon to allow me to execute either projectFolder main.cpp or testProjectA main.cpp/or projectB main.cpp ? 

Edit 1

I'd like to use the projectA with liba.h for example. SO that I can have my main project from main, and test projects using projectAtest ones.

Edit 2 

It seemst hat "Set root project" in cmake to not work as it should. I I open new clion project inside the testProjectA and set the root project to projectFolder, in FMakeList.txt I I can do main.cpp to get that testProjectA main, but if I want to access the library file I have to do ../../libraryFolder/liba.cpp etc. So the root folder seem to not be working as it should?