Navigate to the Turnitin Assignment you wish to edit:

To edit the Due Date or the Assignment Title
Select the three dots to the right-hand edge of that block and select Edit. From the right-hand panel that opens, click in the top field to edit the assignment title. Select the calendar / clock to edit the Due Date and or time. Click on Save at the bottom of the panel to confirm the changes.

To edit the date the Assignment is accessible to students
Select Date/Time. From the right-hand panel that opens, click on the calendar / clock to edit the Date and or time that this assignment can become available to students to access. Click on Save at the bottom of the panel to confirm the changes.

To edit all other settings
Selecting the Title of the assignment opens the Assignment Inbox window. Select the cog from the top right-hand corner:

This will open the assignment settings screen, where you can amend all other fields, apart from those mentioned above:
