The fields configured in a custom module can be added, deleted, or edited.
Field Delete Dependency: If a record has already been created in the end application for the custom module, you will not be able to delete a field. You must first delete the custom record.
To edit the fields of a custom module,
Access the Developer Application.
Select Modules in the left pane.
Hover over the name of the custom module you want to edit. For this illustration, Manufacturers custom module is selected.
Click on the ellipsis icon that appears and select Edit Form Layout. This opens the custom module's field builder.
Make the necessary changes and click Cancel if you have added a field or click Save and Close if you rearranged the field layouts.

Learn more about configuring fields.
The changes made will now be updated in the module.
See Also
Adding and managing custom module and records