Start by seeing if the device is detected:
$ lsusb
Next find the full path of your usb to console cable.
$ sudo dmesg | grep tty
This will give you full device path. For example: /dev/ttySUSB
Next install screen if you do not already have it on your system.
$ sudo apt-get install screen
Now run the screen session against your usb tty device followed by the baud rate:
$ sudo screen /dev/ttyUSB 115200
If you see funky symbols your baud rate is probably set incorrectly. If you omit the baud rate it defaults to 9600.