I have Air handling unit with two inlet water and two outlet, I want to know how to install it with header which coming from chiller. It has only one coil

I believe the coil you have is for both heat and cooling.. one side is for chilled and other is for heated water . So if there overlaped (inside the box) that's what it is, if there side by side ( doughtful) then you need to split both and tie them in that way.