  We present an optical system based on two toroidal mirrors in a Wolter
configuration to focus broadband XUV radiation. Optimization of the focusing
optics alignment is carried out with the aid of an XUV wavefront sensor.
Back-propagation of the optimized wavefront to the focus yields a focal spot of
3.6$\times$4.0 $\mu$m$^2$ full width at half maximum, which is consistent with
ray-tracing simulations that predict a minimum size of 3.0$\times$3.2
$\mu$m$^2$. This work is important for optimizing the intensity of focused
high-order harmonics in order to reach the nonlinear interaction regime.
