Add textframe in framemaker.

#target framemaker
// You need a document object.
var doc = app.ActiveDoc;
// You need a page object.
var page = doc.FirstBodyPageInDoc;
// Add the text frame to the page.
var textFrame = doc.NewTextFrame (page.PageFrame);
// Resize the text frame to the page size.
textFrame.Width = doc.PageWidth;
textFrame.Height = doc.PageHeight;