1) download the file df.m and put it in the work directory.
2) Define the right hand side of the differential equation y' = f(x,y). E.g.,
f = x.^2-y.^2;
3) Specify x-interval and y-interval and the scaling
x1 = -3; x2 = 3; y1 = -3; y2 = 3;
4) save the file df.m
5) At the MATLAB prompt type df