Calculate the matrix element, which is the coupling between the initial and final states. The matrix element is equal to the integral of the interaction between the initial state wave function and the final state wave function. This interaction is written as "V," so the end of the integral expression should be written as "dv" rather than "dx."
Square the matrix element. In other words, multiply it by itself.
Multiply the product from Step 2 by the density of the final states, which is the number of ways in which the transition may occur.
Multiply the product from Step 3 by 2 pi/(h bar). H bar is h/(2 pi), where "h" is Planck's constant. Thus, 2 pi/(h bar) is equal to 4 pi^2/h. The answer that you get is the transition probability.