Vers. 4.7.16. When I go to create a new activity in the WP user interface, the choices in the Activity Type dropdown are limited to 4 options. I want to create more activity types and when I go to Activity Types under Administer, I see lots of existing Types. How do I indicate which of these types (or a new type I create) appear in that New Activity form's activity type dropdown?
Certain activity types are reserved by the system for certain purposes. You cannot directly create an "Inbound Email" activity, for example, because those are created by the email processor in CiviCRM.
You can add new activity types by going to Administer -> Customize Data & Screens -> Activity Types in the menu.