Are you asking about constructing an initial wave function, [tex]\Psi (x,0)[/tex], for a particle in a potential given that information?
If so, what you are describing can be done by using the expansion theorem. Using that theorem, you can express a general time-independent wave function as an infinite sum of the energy eigenstates:
[tex]| \Psi > = \sum_n^{\infty} C_n |n>[/tex]
where [tex]|n>[/tex] is the wave function for the energy E_n and C_n is the probability for measuring that energy.
I can't offer anything more specific given that information, but if you have a homework problem or something similar involving this, please post it in the homework help forum and I'll help you if I can.