You can submit any of your recordings from the Saved Recordings section in the Music Studio.
From there, select the Submit button next to the recording you want to turn in.
You can then link your recording to an assignment from the dropdown menu if it is not linked to an assignment already.
You can then add comments or complete self-assessment before you finally submit (if asked by your teacher).
Once you submit, your assignment has been sent to your teacher. You can edit any of these steps from your Saved Recordings until your teacher grades your recording, then your recording will be locked.