In order for a content type to show up in the “Content create links” area, we need to configure each content type. Let’s configure the “Article” content type for that now.

• Go to “Structure => Content types => Article => Manage fields” (admin/structure/types/manage/article/fields)
• Click “edit” next to “Groups audience”

If we scroll down just a bit, we’ll see the “Additional Behaviors” section. In here, we need to enable the “Entity reference prepopulate” option for this content type to show up in our “Content create links” list.