The team behind the project doesn't seem like it has any plans to do an airdrop[1]. The blog article you're reading is supposed to prepare you for a "potential airdrop" but that's not going to help either now that the mainnet has launched.

[1] https://www.coindesk.com/tech/2023/03/24/matter-labs-has-no-plans-for-zksync-era-airdrop-but-crypto-twitter-is-speculating/