You can't do it in Basic.

You can transfer the file to Professional (or just change the directory to open and save in the 24BasWin Data file).  Split it (see link).  Then transfer the two files back to Basic (if you change the directory in Professional, they may already be there).  You may need to do "Homebase Maintenance" in Basic after you put the new files there.

https://accountants.intuit.com/support/en-us/help-article/tax-filing-status/splitting-married-filing...