You will need to create an alby address. The guide does a redirection from billy@adnostr.com to billy@getalby.com
Discussion
I have a similar guide here that explains in detail if you want to have a look at it https://orangepill.dev/lightning-guides/guide-to-create-lnaddress-redirection-on-your-domain/#how-to-setup-lightning-address-redirection-with-your-domain-using-github-pages-to-redirect-to-wallet-of-saotshi-or-getalby-lightning-address-free-and-easy