It is important to first familiarize with the software. Try to make it run on your device/machine.
Look at the list of all the Open Food Facts projects:
https://github.com/openfoodfactsOnce you're able to run it, try one of our "good first issues" on GitHub (also accessible from this list).
If you have not worked before with Git Branching, we encourage you to visit this web:
https://learngitbranching.js.org/