Hey @capgos17
Firstly, it’s awesome to hear that you want to contribute to Rasa Open Source!
To get started with code contributions, it would be best to check out this guide: How to make a code contribution.
As mentioned in the guide, it’s important to first consider if you want to contribute to an existing issue, or work on a potentially new feature. Both of these options are covered in the guide, however, our contributor dashboard on Github is also a key resource to help you check current open issues we’d like support with.
We also have a contributor program, designed to recognise efforts and achievements within the community. Since you plan on starting your contributor journey soon, I definately encourage you to take a look at those perks too. 
Hope that helps, let me know if you have further questions.