Blessed [be] the God and Father of our Lord Jesus Christ, who hath blessed us with all spiritual blessings in heavenly [places] in Christ:
Note 1 at Eph 1:3: After a short greeting, Paul got right to the point. He started praising God for the great spiritual blessings that we already have in Christ. This is his theme throughout Eph 3.
Note 2 at Eph 1:3: The phrase "who hath blessed us" is in the aorist tense in the Greek; this means that there was a point in the past when all these blessings were obtained and given to us. Paul was describing what is already ours. These are not blessings to be sought after but rather blessings to be discovered and enjoyed. We who have put our faith in Christ are not headed to a victory; we are coming from a victory that is already accomplished.
Note 3 at Eph 1:3: "In heavenly places" carries the idea of in the spiritual realm (see note 25 at 1Co 14:37). "In Christ" we have been blessed with all spiritual blessings. These things are now spiritual realities. Our spiritual selves are already complete (see note 3 at Mt 26:41). As we believe and act in faith, these spiritual blessings become physical realities (see note 50 at Mt 7:8).
The phrase "in heavenly places" is used four times in this letter to the Ephesians (this verse, 1:20; 2:6; and 3:10). In the other three references, it is clear that Paul was speaking about real places that are beyond the Earth's atmosphere.
Here is a partial list of some of the blessings that Paul mentioned in the first two chapters of this letter: We have been adopted as God's children (Eph 1:5), we have redemption through Jesus' blood and the forgiveness of our sins (Eph 1:7), we have obtained an inheritance (Eph 1:11), have been sealed with the Holy Spirit (Eph 1:13), have been given the same power that raised Christ from the dead (Eph 1:19-20), have been made the one new man (Eph 2:15), have been made fellow citizens with the saints and of the household of God (Eph 2:19), have become a holy temple in the Lord (Eph 2:21) and a habitation of God (Eph 2:22), etc.