Through the custom field module, the administrative user can make changes to custom field names and delete custom fields. You will not be able to edit field values for picklists or multi-select picklists in this area of the application. Field Value editing for picklists is done in the Picklist Editor. If you're trying to make changes to picklist or multi-select picklist values, view the video on the Picklist Editor.
Similarly, you are not able to change field properties once the field is created. If you need to change field parameters on a Field that is a number type, for example, you will want to recreate the field and then map over values with correct formatting using the import process. Please view administrative guides on Importing for more information.