- on your website, add a “add to anki” functionality, this simply marks the word in your internal database.
- develop an anki addon (specific to your website) to sync from your website to add those words into anki.
It would be difficult to directly add to anki in one step. Because people have their own note types, fields, decks, etc. Your website will simply be unaware and will have no way of knowing where and how the user wants to add that note. That logic is best handled in Anki.
Don’t be intimated by that second part. If you’re a developer, you can develop an Anki module, as simple as that.