Cross-post to a Mastodon account:
@you@mastodon.server

      
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You have a Mastodon account. You want to post on your web site, copy those posts to that account, and send responses back to your site.

Connect directly to the fediverse:
@yoursite.com

   
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 — 🌐 — 
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Your web site will be its own fediverse account, including its posts. Its username and instance will be your domain. This takes a bit of technical known-how.