Hi Chuck, glad you got it working. So /mnt/4GB.swap none swap sw 0 0 is meant to be added to the end of your /etc/fstab. You can do that in a text editor - the Nano editor is easy to use:
$ sudo apt-get install nano
$ sudo nano /etc/fstab
# scroll down add add this line to the bottom: /mnt/4GB.swap none swap sw 0 0
# Press Ctrl+o to save, then Ctrl+x to exit
$ sudo reboot
After rebooting, if you run tegrastats, you should see at least 4096MB of SWAP memory listed.