The proportions are:

The proportions are: 1/3 espresso, 1/3 milk, 1/3 the foam you get with the steam spout.

Fill a metal jug with cold milk to 1/3.
Immerse the steam spout in the milk and enable the jet. When the foam rises and the milk volume rises, lower the pot always holding the spout’s tip submerged.
It is important that the milk volume does not rise excessively; avoid creating large bubbles.
Leave to rest…

Beat the bottom of the jug on the tabletop several times to eliminate any air bubbles.
Prepare an espresso in a large cup.
Pour the milk into the cup carefully modulating the flow.