I am a complete novice and know nothing about coding. I have several websites and use the Atahualpa theme for two of them. I had a problem with permalink showing up on my home page for counselingforweightloss.com so found a post here that told me how to make changes to bfa_post_parts.php. I got cocky and went in and made a change and now have a new problem because I "fixed" the wrong line. I didn't save a copy of the old file and I don't know how to update it and start over.

Any advice on how to correct this problem would be appreciated.

Just upload a fresh copy of the file you changed via FTP. I never edit the theme files as the edits won't survive a theme upgrade unless you document exactly what you did. There are generally ways to do most anything without modifying theme files.