Answer:
By reducing the focal length
Step-by-step explanation:
The power of a lens is inversely proportional to its focal length.
Mathematically, this relation can be written as

Where, "P" represents power and "f" represents focal length. As per this relationship, the power will increase with the decrease of focal length.
Power is basically the measurement of refractive power of a lens. The refractive strength of a lens increases with the decrease in focal length.