Welcome! And a big thank you for wanting to contribute!
Let's get you started. First of all, this project is licensed under the Apache 2.0. This means that the code you submit will be usable for anyone for any purpose free of charge. Please submit code that you personally own or have permission to submit under this license, and only if you are ok with that.
That's out of the way, let's focus on making your contribution happen. For the coding aspects we recommend reading the development guide. It runs you through the nitty-gritty details of setting up the development environment.