I think you meant you want to plot f(t)=at^2+bt+c in Simulink since you mentioned parabola in your answer. Although you can use MATLAB function block inside Simulink and create the same function as MATLAB, but it appears that this is not what you are trying to do. The block diagram to do this is Simulink using basic blocks is given below
The Simulink model file is also attached. Run the simulation and open scope to see parabola.
