This is stated here (Eph. 2:6). Although in a spiritual sense Christians can enter this place now by the measure of faith they’ve been given, still it remains for all believers to physically sit there. When this eventually happens, we will enjoy the fullness of God’s purposed privilege and blessings for us in Christ (Eph. 2:7). At that time the glorified church will be blessed with every spiritual blessing in the heavenly places (Eph. 1:3). The church’s heavenly calling and spiritual blessings in heavenly places is a direct contrast to the earthly calling and promised physical blessings of the Jews.
Additional information on why and how the Christian will sit in Heavenly places: