@User this is a schematic showing the circuit. you open it in xchem. Xschem can generate a spice netlist from this circuit and the spice netlist can be simulated by ngspice. In this workflow xschem is a frontend graphical program allowing you to draw, see, edit a circuit and send the circuit netlist to ngspice for simulation. Another approach is to get directly the circuit spice netlist in some other way and launch ngspice on it.