Solve Initial Value Problem given General Solution.

Im having a little trouble with these problems. Im sure its pretty simple. Heres one from my book:

**Given the family of functions is the general solution of the differential equation on the indicated interval. Find a member of the family that is a solution of the initial-value problem. **

$\displaystyle y = C1e^x + C2e^-^x, (-\infty, \infty)$

$\displaystyle y'' - y = 0, y(0) = 0, y'(0) = 1$

Can someone show me how to do this problem? I am just confused one how to work it. Im sure its pretty simple but I cant seem to figure it out.

Thank you!