Ephesians 1

In my mind, the epistle to the Ephesians was one to members that had been taught a great deal of pure doctrine and the mysteries of God and must have remained faithful in obedience and understanding, because Paul begins his epistle with -

"Blessed be the God and Father of our Lord Jesus Christ, who hath blessed us with all spiritual blessings in heavenly places in Christ:
4 According as he hath chosen us in him before the foundation of the world, that we should be holy and without blame before him in love:
5 Having predestinated us unto the adoption of children by Jesus Christ to himself, according to the good pleasure of his will,
6 To the praise of the glory of his grace, wherein he hath made us accepted in the beloved."  (New Testament | Ephesians 1:3 - 6)

It is obviously clear to me that Paul is referring to our pre-mortal existence.  In my mind, it is clear that we lived as literal spiritual children of our Heavenly Father before this life in "heavenly places".  It was there we learned and exercised repented and faith in the Lord Jesus Christ and His atonement long before the infinite atonement was satisfied.  Much like in this life many received the blessings of the atonement even before the Savior was born.  Elder Jeffrey R Holland -

“We could remember that even in the Grand Council of Heaven He loved us and was wonderfully strong, that we triumphed even there by the power of Christ and our faith in the blood of the Lamb.” (Jeffrey R. Holland, October General Conference, 1995)

LDS Institute Manual also teaches concerning this pre-mortal existence -

"We were given laws and agency, and commandments to have faith and repent from the wrongs that we could do there....Man could and did in many instances, sin before he was born.” (The Life and Teachings of Jesus and His Apostles, p . 336)

We were there "foreordained" through our faith in Jesus Christ, there and now, that through His atonement we would become "adoptive" sons and daughters of Christ from perspective that through Him we have "eternal life".