Please help, construct a natural differential structure on this manifold

saminator910

I need to construct a natural smooth differential structure on the ellipsoid [(x^2)/(a^2)]+[(y^2)/(b^2)]+[(z^2)/(c^2)]=1
So I need an Atlas to produce this, how would I do this? I don't really have an idea of what functions and sets an Atlas consists of, can one use parametric equations? Also, is this diffeomorphic to S^2? There needs to be a smooth mapping from the ellipsoid to the 2-sphere, correct?