When hhaving that activated you have an app folder called Linux in that there is a terminal. That will you need. In the terminal you need to download the source code. Run in the terminal "sudo apt install git libeigen3-dev libsfml-dev make cmake" to install the dependencies. Now run "git clone https://github.com/HackerPoet/MarbleMarcher" to clone the git repo. Then "cd MarbleMarcher" to open that folder and then execute "mkdir build && cd build" to create a new folder and open it "cmake .." to setup the build system "cd .." to get back to the root folder "cmake --build build" to build it
