Wife not having SSN or ITIN

I have my tax returns file ready to mail thanks to TurboTax, but I am here on H1b visa and my wife is on H4, so she is not having SSN or ITIN. I am filling "married filling jointly". So what should I mention instead of her SSN ? I am thinking to go for her ITIN. So do we need to file first and then have to go for ITIN ? or first get ITIN first and then file taxes? Whats the  exact roadmap?