Being in the light has nothing to do with being religious or serving God. It just simply means being a new creation in the new covenant.
The bible speaks about the law and the instruments in the tabernacle of Moses as the shadows. These shadows points to a reality. This reality is Christ. If you believe in Jesus, you are in Christ. You are in this reality. You therefore move from the shadows into the light.
The bible also tells us in the Amplified version that you are the very sanctuary of the Holy Ghost. You are not the outer court nor the inner court, but the very sanctuary meaning the Holy of holies of the Holy Spirit.
In the holy of holies, there is no window. The only light comes from the glory above the ark. You are that holy of holies. Christ lives in you. You are no longer of the law and its tabernacle. They are merely shadows. You are now in the reality they point to. You are in Christ and Christ in you.
That is how you enter the light and how the light of all men makes you the light of the world. When you enter the New Covenant.