How to include own css on wordpress tinymce editor?

I have added some text on tinymce editor on load.
(Every time you click on Add new the tinymce editor load with this text.)

but problem is how to enable css class which are using in default text.

Thanks

Use add_editor_style

e.g.: functions.php

add_editor_style('custom-editor-style.css');

http://codex.wordpress.org/Function_Reference/add_editor_style