Work or energy is the vector dot product (one form of vector multiplication) of force (which is the product of mass and acceleration) and distance traveled.
Power is energy spent per time.
1) increase power used by increasing mass. more mass means more force and therefore more power used.
2) increase the speed or acceleration. That also means more force.
3) make the stairs steeper. That means that more force is required to translate into the same distance and therefore more power.