To participate and earn the free $100 USDT, you can follow these steps:

1. Access the "Lite Referral" feature through the referral section of your Binance account.

2. Once you're there, a banner will appear. Click on it and you will receive up to $40 USDT for free.

3. To reach the $100 threshold, you need to refer a few people using your lite referral link.

4. After reaching the $100 milestone, you can click on the withdraw option to claim your money.

Please note that the information you provided does not guarantee the availability or accuracy of this promotion, as my knowledge is based on information up until September 2021. It's always a good idea to double-check the latest promotions and terms directly on Binance's official website or contact their customer support for confirmation.