Since you have been here in the USA for all of 2018, you would be treated as a dual status taxpayer ( ditto for spouse because she is on a subservient visa). To file MFJ, you need to add a request that you wish to be treated as a resident for the whole of 2018 -- should not have any detrimental effect on you or your spouse. You prepare your return using TurboTax as a resident, print, date, sign( both of you ), include a note requesting to be treated as a resident for all of 2018 , and mail this in ( instead of e-file). That is all
hope this helps
