If you need to make changes to the operations of any Make Items or their sub-assemblies, a great way to do so is through the "Edit Operations Mode" in the Make Item's Bill of Materials tab.
In order to reach this page, navigate to Items -> Make Items....
Select an Item...
... Click on the Bill of Materials tab...
... then toggle Edit Operations Mode.
After toggling on Edit Operations Mode, you can click any of the operation pills to view and edit details regarding this operation, including:
Operation Name
Process
Setup time
Run Time
Run Size
Run Rate
Default Work Center Assignment
Default User Assignment
Input Parts
Operation Notes
When you're ready, click "Save Changes" to retain the updates made.