To add this to the serenity OS system, you have to build the port for it.
Copy platforms/serenity/package.sh to Ports/oopetris/package.sh, create the directory Ports/oopetris/ and add the file to it.
Then just cd into the directory and run the package.sh, like with all other Serenity OS ports.
We don't have a CI for this port, so please report errors, if you find some.