Where did you see this online? Why not ask there?
I have never come close to pulling it off, but in theory it is straightforward. You need 44+ paratroopers, 11 nuclear subs, and 11 nuclear missiles. But if you have that kind of capacity, why have you not already won? It takes a couple of turns. You also need line of sight on the 11 caps, which hopefully the subs+ spies can provide. This might not be possible on a huge map because XCOM drop range is limited.
T-2: Unlock Nanotechnology, upgrade the 44+ paratroopers to XCOM.
T-1: DOW and drop your 11 nukes on 11 caps. Drop 4+ XCOM per cap. (XCOM cannot attack on the turn they drop unless they have the Blitz promotion.)
T0: Each group of 4+ XCOM takes a cap. If the AI has tech parity, 4 XCOM per city is probably not quite enough. Or maybe the city assault takes a couple of turns.