Fortunately, as with other server software on the OS X, I can actually enable the FTP server using the launchctl program on the Mac.

The launchctl software interfaces with launchd (a software that runs on the background to manage daemons/agents on the Mac) daemon on OS X.

Launchctl allows Mac users to load, unload daemons/agents and generally control launchd. To load the FTP server, just run the Terminal app and run the command:

sudo -s launchctl load -w /System/Library/LaunchDaemons/ftp.plist

And just like that FTP is now enabled.

You can unload the FTP server by also using the launchctl command. To unload the FTP server, just perform the following command in the Terminal app:

sudo -s launchctl unload -w /System/Library/LaunchDaemons/ftp.plist