Navigate to the Gradebook tab from GO! dashboard. 

Then, the teacher can select any specific class from the Classes dropdown. 

After selecting the class, select the assignment that needs editing.

To edit/modify assignments in the Gradebook, click on the assignment title and then choose Edit option from the Assignment Manager menu.

Upon clicking on Edit, teacher will be navigated to the Edit Assignment screen.The teacher is allowed to edit the general Assignment and Additional Information such as start/due dates and times, display Future status, etc.  

After making any changes, make sure to scroll to the bottom of the screen and press the blue Save button.