This homebrew, in case you're a first-time reader, is a PSP port of ADoomPPC. It's ported by Chilly Willy
and is one awesome FPS homebrew that you can run on HBL perfectly

Installing:
1) run OpenCMA on your PC, and CMA on your Vita
2) copy the previously packaged SAVEDATA with your homebrew in “install.zip” on your Vita
3) run HBL
4) navigate with the HBL menu to the SAVEDATA folder, then go to the folder you just downloaded (UCUS12345000),
and click cross or circle on it
5) At this point, the HBL menu should ask you if you want to install the homebrew. select yes, and wait until HBL is
done extracting your homebrew
6) The homebrew is now installed, and you can run it by going to the GAME folder, if everything went well, a new
subfolder with your homebrew has been created here, and you can run the homebrew