To enable and opt-in you follow this account: @bsky.brid.gy@bsky.brid.gy
That will start mirroring and federate your ActivityPub account over the ATProtocol and assign a DID.
Then the counterpart for BlueSky you follow: https://bsky.app/profile/ap.brid.gy
And it will start mirroring your ATProtocol account as an ActivityPub account.
AT to AP seems more seamless since AP has more features. Truncating long posts for example looks ugly. The plan is to thread them eventually.
gombang