When you signup, there's a walk-through. You'll end up with an email-like address (eg. example@getalby.com), then you can post that to nostr, and other social media. To turn your lightning into fiat, you can purchase a visa debit card from @The Bitcoin Company or

Bitrefill

Buy Gift Cards & Top Up Airtime with Bitcoin or Crypto

Bitrefill (United States) - Shop for Gift Cards, eSIMs, and Mobile Recharges with BTC, ETH, USDT, USDC, and more. Pay online with crypto in over 18...

or use #asknostr with your question, and users'll give you help.