To edit the details of an item, click on the specific item (a work order, tool, material, etc.) and you will be directed to the item's detail view.
Locate and click on the "Edit" button (usually in the top right of a section).
When you are done making changes in the edit view, press "Save" at the top right of the form.
Editing from an item's detail page generally provides more options than editing from the list view. For more on list functions, see List functions in Basics.