You should use your address abroad, even though the form isn't well-designed for this and appears to give room only for a U.S. address. Though you are not eligible to file this form if you reside in the United States, the IRS doesn't provide room on the form for a foreign address yet the way that they do on many other IRS forms.
Since the form has to be submitted by mail, you can handwrite your foreign address to fit in the area provided.
You should also provide your foreign phone number - just remember to include the country code and to write it in a format for dialing from the U.S.