If you loaded the assignment from an LMS then you will have the option to download the standard assignment file. From there, the assignment should load with the embedded launch code. If a launch code is not found in the embedded file, you can manually load the assignment by copying the launch code from the assignment page into the add-in text area.
Assignments can be graded and submitted using the Grade Result slideout. To open the slideout, click the grade result button in assignment toolbar. On the Grade Result slideout, you can use the Grade button to grade an assignment which will allow you to see your results before submission. After you have graded an assignment, the Submit button will enable allowing you to submit your assignment for a grade and pass that submission to your course.