First, you have to create a task by typing
/assign in the message box followed by the Task name and press Enter button.
After pressing on the enter button a dialog box will be displayed. Here you can add a due date & time and the assignees of the task or you can also assign the task from the ‘Actions‘ tab after creating the task.
Your assignee can quit yourself from a specific task, Go to the channel and click on the ‘Actions‘ tab of the selected task and click on the ‘Assign to‘ button. Now select the member to which you want to unassign from the task.
( For example – If you want to unassign Ethen Hunt from the task ) Click on that name.
After clicking on that name, you will see a notification on your screen with the unassign button. Click on that button.
That person is successfully unassigned from the task.