newbee234:
The connect power of the arduino was crossed out in the instructions above.
Correct. It's impossible to perform a loop-back test unless the board is connected to the computer. If the board is connected to the computer, it is reasonable to use the computer as the source of power.
Does that mean the arduino does not need an external power supply when just the base unit is plugged into the computer?
I don't know what a "base unit" is but I'm going to say "yes".
It is not mentioned anywhere on the web site!
Of course it is. Search for the Power section...