I was married in March this year how do I change my last name with turbo tax

Here's some general info on getting married.  Did you both use Turbo Tax last year?

You can not transfer from or combine 2 returns or accounts.  Just pick the return for the spouse that has the most complicated return to enter or has any depreciation or business or  more investments.  Or use the account for whoever you want to be listed first going forward (by the way you can not change the order of the names).  Then add the other spouse's name, ssn and info to it.

You should usually  file a Joint return which is only 1 return combined for the both of you.  Make sure to stick with this one account for the future.  Just ignore the other spouse's account.

Getting Married FAQ

https://ttlc.intuit.com/community/tax-filing-status/help/what-does-getting-married-mean-for-my-taxes/00/1756642

And info on Getting Married…..

http://turbotax.intuit.com/tax-tools/tax-tips/Family/Getting-Married/INF12006.html

Is it better to file Joint or Separately?

https://ttlc.intuit.com/questions/1894449-is-it-better-for-a-married-couple-to-file-jointly-or-separately