We are in Christ and yet we read that Christ is in us. We are in Him because we are believers who shall not perish, but have everlasting life. We are the body of which he is the head, and we are part of the perfect Bridegroom, and have been since the foundation of the world. I don't understand it, but I believe it. The only thing that I can think of to help us understand is that you should imagine that there is no Time.
Time is something which has been injected into the Eternities.
We read in God's Word that Time shall be no more.