Not enough power driving wheels of 2wd arduino robot!!!

Ok, so I'll repeat. I'm new to ALL of this. here is the kit I built.....

http://www.ebay.co.uk/itm/160880393469?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649

I followed all the correct instructions, I use a 9v battery to power the Arduino and 4x1.5v battery pack for the motors.

as far as the current getting to the motors< I don't have a clue??? Sorry.

If any of this is of help and you can advise me, thank you.