The exercises are submitted to GitHub, and by marking the exercises as done in the exercise submission system. You can read more from here.
Frequently asked questions
No. You can use one or more repositories, most important is to name everything in a repository clearly.
No. All exercises for a part must be submitted at the same time. If you marked exercises wrong by accident, or wrote the repository name wrong, send an e-mail to matti.luukkainen@helsinki.fi.
No, but there shall be a open version of the course starting at 15th March here!