Set default text format for a content type At "Home » Administration » Configuration » Content authoring"
I added a custom text format (news).

Now when I trie to enable this for a certain content type "Newsmessage"
"Home » Administration » Structure » Content types » Newsmessage » Manage fields"

I only see  "Plain text" or "Filtered text (user selects text format)" as options. 
How do I set the "news" text format as a default for my "newsmessage" content type?
If the field is Wysiwyg, so you might want to configure the "Wysiwyg" profile settings, then it will be available in the Structure » Content types » contentType name  » Manage fields.