Have you setup a config file? Also when you do backtesting you don't need a paper trader (paper traders are live traders that trade with fake money on the exchange... nothing to do with back testing)
UPDATE: If you are kinda new to Gekko and want to use it on the command-line for backtesting, this video might get you started https://www.youtube.com/watch?v=p65mH9ogenc
UPDATE: If you are kinda new to Gekko and want to use it on the command-line for backtesting, this video might get you started https://www.youtube.com/watch?v=p65mH9ogenc