// Add a class to all paragraphs in the editor.
tinymce.activeEditor.dom.addClass(tinymce.activeEditor.dom.select('p'), 'someclass');

// Gets the current editors selection as text
tinymce.activeEditor.selection.getContent({format: 'text'});

// Creates a new editor instance
var ed = new tinymce.Editor('textareaid', {
    some_setting: 1
}, tinymce.EditorManager);

ed.render();