Where can I find the code for submitting the project?
You pick your own code. It has to consist of 5 digits - letters, numbers or their combination. When you submit your project you will be able to see whether the code is still available - if there already isn't a submitted project bearing the same code. Because of this, we recommend submitting your project via website first and then via regular mail (in which you include the same code).
and join the challenge!