how to plot the audio into sample?

clc;
clear all;
close all;
fileName='Voice_002.wav';
[y, fs, nbits]=wavread(fileName);
N = length(y);% % N is the number of samples
sound(y, fs);    % Playback of the sound data 
time=(1:length(y))/fs;  % Time vector on x-axis 
plot(time,y);xlabel('Time');
ylabel('Amplitude');    % Plot the waveform w.r.t. time 
fprintf('Information of the sound file "%s":\n', fileName);
fprintf('Duration= %g seconds\n', length(y)/fs);
fprintf('Number of samples %g:\n', N);
fprintf('Sampling rate = %g samples/second\n', fs);
fprintf('Bit resolution = %g bits/sample\n', nbits);

[Walter Roberson]

? Your line

plot(time,y)

already appears to be plotting the samples.