Where could I file an ITIN? (I am a spouse of an alien resident- Im under H4 visa) is it only through mail? Can't I visit an IRS office to apply for that? How long would I have to wait for ITIN?

File W-7 (ITIN application) with your tax return. Do not file separate W-7. Mail it to Internal Revenue Service, ITIN Operation, P.O. Box 149342, Austin TX - 78714-9342