Hi James,
For plotting multiple normal distributions overlaying each other probably you can use the hold on keyword present in MATLAB.
you can use it as.
x1 = [1 2 3 4 5];
y1 = [2 4 6 7 10];
x2 = [5 4 3 2 1];
y2 = [2 3 5 8 10];
plot(x1, y1);
hold on
plot(x2, y2);