First, select Assessments from the left-hand navigation.
To access your item bank, either begin to create a new advanced assessment, or edit an existing one and scroll down to below the item list.
Select the item that you would like to remove by clicking the title of the item, and then the "Edit" button that appears in the Item Preview popup. If the item has already been added to an assigned assessment, you will receive a warning that tells you the changes you make won't carry over to assigned assessments.
Select Delete Item