How do I give myself permissions to edit files in my Wordpress theme via FTP?

Question

I am using Filezilla right now to edit my Wordpress JS and CSS theme files since I prefer to use Atom to edit than the default Wordpress text editor, however I am getting a Critical file transfer error. I thought this was due to permissions but the chmod is set to 644 and I believe I am running from the admin account. Furthermore, I can edit the wp-config.php file which is also chmod 644. I also have read somewhere that it may be that theme files Wordpress being blocked from FTP transfers.