how to overlapp and add the frames after applying some modification in time domain

I am trying to apply Dynamic range compression (DRC) in time domain in matlab. But I am having problem in overlapping and adding the frames. Somebody please help. Here is my work-

    [x,fs] = audioread('1.wav');

   windowLen = 512;    % Window length in samples

   start = 1;          % Window start index 

   halfwin = windowLen / 2;    % Half window for calculating overlaps

   win = hamming(windowLen);   % Generate window

   frames = floor(length(x)/halfwin)-1;    % Calc number of frames in x

   % --- process frames ---

   for i =1:1:frames

       m=1;

       signal = y(start:start+windowLen-1);  % Samples in current frame

       winsignal = signal .* win     % Apply window function

       ------process winsignal by applying DRC-----

   start = start + halfwin;  % Move to start of next window 

   end

Now i don't know how to overlapp and add these processed frames (winsignal) for getting my desired output signal. Any kind of improvement in above code or further help is appreciated. Thanks in advance