In OSX, turn on the terminal, plug in your FTDI USB-serial dongle, you should see a new usbserial device created under /dev. Use "screen" to start the session, remember to state the baudrate at the end of the command:
$ screen /dev/cu.usbserial-FTVLVQ6M 115200To detach:
Ctrl-a dTo re-attach:
$ screen -rTo kill the screen:
Ctrl-a k