fsk with flat fading

Hello evry one

I have this 10 bit fsk signal and i want to add flat fading to it please any one can help me , or to rewrite anew code of fsk signal that easy to add flat fading

 n=randi([0 1],1,10); 
    j=1;
    t=0:.005:length (n);
    for L=1:length(t);
        if t(L)<=j
        y(L)=n(j);
        else
            y(L)=n(j);
            j=j+1;
            
        end
    end
       f1=3;
    f2=5;
   y1=sin(2*pi*f1*t);
   y2=sin(2*pi*f2*t);
for j=1:length(t)
if y(j)==1
    z1(j)=y1(j);
else
    z1(j)=y2(j);
end
end

to it?