The only change you need to make to start sending your bundles to the Archer relay is to pass in the Archer relay URL when you call "FlashbotsBundleProvider.create" like so:
const flashbotsProvider = await FlashbotsBundleProvider.create(provider, authSigner, 'https://api.archerdao.io/v1/bundle')
See demo.ts for an example.
See our docs for more details about Archer Relay