Nice -- your function is already in "vertex" form, so there's not a lot of calculations to do. So here's what you need to know: Vertex form of a quadratic function is y = a(x-h)^2 + k. When given in this form, the vertex is found at (h,k), and the axis of symmetry is x = h. Applying this to your problem, we have f(x) = -1*[x - (-3)]^2 + 9, and h = -3 and k = 9. Thus, the vertex is (-3,9), and the axis of symmetry is x=-3.
To reinforce your understanding, it may be helpful to read up on the webpage and video tutorials listed below. I've also included an online graphing calculator so you can more easily check your answers.
If you need more help, please clarify where you are in the process and what's giving you trouble. I'd be more than happy to continue to assist.