Answer
crush the cubes of broth, add warm water and stir the container.
Explanation
The FASTEST way to make the chicken broth with the cubes you have will be to increase the surface area of the cubes broth by crushing and raise the temperature of the cubes broth by adding warm water and by stirring the container.
Hence, the correct answer to your question is:
crush the cubes of broth, add warm water and stir the container.
