Mandritto sgualembrato is a diagonal cut descending from the right side. It is the most fundamental of all cuts in the system. While the cut can be performed with any type of step, it is most often done with a passing step of the right foot.
As your very first cutting exercise you should practice the mandritto sgualembrato with a passing step, done both as a half-cut that end with the point in presence, in porta di ferro alta and as a full cut traveling through into porta di ferro larga.
Typically you start from coda lunga stretta with the left foot in front, and as you execute the cut you begin by lifting your hand into guardia d'alicorno, then turning the point backwards as you begin to pull yourself forward into the step, moving through guardia alta and then delivering the cut as you pass forwards, either into porta di ferro alta as a half-cut, or larga as a full cut, or sometimes even to guardia sotto il braccio, but that is more often done when fencing with a buckler.
These cuts can be prepared also by going directly into guardia alta or by throwing a tramazzone or a molinetto. While the these two would still be considered mandritti sgualembrati when traveling on the diagonal line, optimally aimed so that it travels from the left side of the opponent's neck towards their right knee, they are special cuts due to the way they are initiated.
First learn to do the mandritti with big, clean motions, studying the guards they travel through. When passing guardia alta, make sure to align the edge towards the target and cut done along its plane; too wild a rotation above the head could easily lead to a misaligned strike with the flat.