When I login with Facebook account that have same email with a ACS account (created before by app).
How can I integrate this Facebook account with my ACS account?
For this you need to implement the Facebook Module to provide a login-via-Facebook button and retrieve their access token. Then use that to call the ACS/ArrowDB users/external_account_login endpoint with tho log them into ACS/ArrowDB with that.
For this you need to implement the Facebook Module to provide a login-via-Facebook button and retrieve their access token. Then use that to call the ACS/ArrowDB users/external_account_login endpoint with tho log them into ACS/ArrowDB with that.