The word "manifestation" means to make visible. Many things about our lives can be seen by the watching world we live in. When we are angry, happy, joyful, or grieving our body language can reveal so much about what we are feeling without saying a word. 
But Scriptures tell us that we are to manifest the presence of Christ to a watching world. We are a new creation in Christ, the old things are passed away, and behold new things have come.  We are to be continually transformed into the image of Christ from faith to faith. God is working out the fullness of His presence in our lives if we are truly followers of Him. 
This manifestation of Christ is not accomplished by human effort but by human surrender to the Holy Spirit in us.  He must increase and we must decrease. We are not to seek self-exaltation but die to ourselves that Christ may be exalted in us and through us. 
We are not to seek our kingdom but the Kingdom of God in which Christ rules and reigns in our hearts and manifest Himself as a sweet aroma to  God!