B747 Captain reported a loss of aircraft directional control during the takeoff roll resulted in a rejected takeoff.

Narrative

I was giving a new hire student instruction on Aircraft X. It was his first operating leg in a -8. We were cleared for takeoff Runway XX in ZZZ. He taxied us into position for takeoff. We appeared to be lined up straight for takeoff. I asked if he was ready for takeoff. He and the rest of the crew all said they were ready. I stood up the engines for takeoff. Once they were stable I pushed the toga switch. As we started rolling the aircraft drifted right. I announced steer left. I believe the first officer used either the tiller or the rudder to steer us back.We immediately received a body gear steering takeoff warning. I rejected the takeoff and cleared the runway. We were at approximately 20 knots at most. We taxied back to the runway for takeoff. We were well above minimum fuel. Once we were cleared for takeoff again; I demonstrated the proper procedure to line up on the runway. We had a normal takeoff with no further issues. First Officer didn't align the aircraft properly and didn't correct the misalignment properly during the takeoff roll. I need to ensure the body gear is straight before applying takeoff thrust. If the cause was due to the first officer not correcting properly; I should take the controls from him quicker.