All helis will want to go left on takeoff due to the rotational torque of the main rotor. Are you trying to take off slowly? If so, pop it up in the air quickly and it should go into a stable hover.
If not, initialize the heli and let it sit on the ground without moving the sticks. Check that the swashplate is level, if it isn't, it will want to go in the direction in which the swashplate tilts. To level it, lengthen or shorten the rods from the servos to the swashplate until it's flat and level. Report back with results
