If you have 2 functions f(x,y) and g(x,y) you can evaluate the product on your selected grid-points and multiply them:
fx_at_xy = f(x,y).*g(x,y);
or you can create a function that multiplies the two:
f_times_g = @(x,y) f(x,y).*g(x,y);
and use that one - this should (at least ought to) be more convenient when for example integrate over some region in the x-y-plane.