1 | initial version |
Unfortunately that's an area of the documentation that is out of date and refers to the old and obsolete GTK UI.
In the new UI, most fields are actually a drop list, activated by clicking on the field. Use the "current" field to select the protocol you wish to use. Click "OK" to just set the decode options for the current Wireshark session, click "Save" to save them to the current profile for use in subsequent sessions.