Welcome to the Math Help Forum!
To find the point on closest to , we first do as VonNemo said and use the distance formula to obtain a function of the distance from a point on the curve to as a function of :
We now find the value of for which is a minimum. To do this, we differentiate and find all critical points. As is differentiable everywhere and has no boundary points, the only critical points will be those at which . As approaches infinity in both directions of the -axis, at one of these critical points we must find our minimum.
Hope this helps!