Depending on the way the assignment has been set up by your course team, it might be the case that it has automatically been submitted to a workspace in ATLAS, especially if your assignment is using a template such as a workbook resource.

You can check on whether your work has been already submitted by looking in your Asset Store and seeing if the clipboard icon is lit up with a number next to it:

Clicking on this and then scrolling down to the ‘SHARED FOR ASSESSMENT’ section should tell you where it has been submitted to.

 If you are unsure or it hasn't automatically been submitted, please contact the Library.