Help with FFT Analysis

Hi,

How could I use the fft analysis on this signal:

I am trying to find which filter would be the most ideal to get as close to the original signal as I can.

% Signal Generation

xLim = 1000; % Generate numbers from 0 to 1000.

dx = 0.01; % Increment of 0.01.

x = 0:dx:xLim-1; % Generate a series of numbers from 0 to 999 (xLim-1) with increment of 0.01.

y0 = 6*sin(0.4*pi*x); % Create sine signal.

y = awgn(y0,0.01,'measured'); % Addition of noise

% Filtering of Noise using Savitzky-Golay

N = 2;

% Filter 1 F = 11; % Window length 11,23,35,47,59

[b,g] = sgolay(N,F); % Calculate S-G coefficients

HalfWin = ((F+1)/2) -1;

for n = (F+1)/2:(length(x)-5)-(F+1)/2,

% Zeroth derivative (smoothing only)
  SG1(n) = dot(g(:,1),y(n - HalfWin:n + HalfWin));

end

% Filter 2 F = 23; % Window length 11,23,35,47,59

[b,g] = sgolay(N,F); % Calculate S-G coefficients

HalfWin = ((F+1)/2) -1;

for n = (F+1)/2:(length(x)-5)-(F+1)/2,

% Zeroth derivative (smoothing only)
  SG2(n) = dot(g(:,1),y(n - HalfWin:n + HalfWin));

end

At the moment I tried to use: A1=fft(SG1); A2=fft(SG2);

Not really sure how to apply the fft coding and if I am doing it correctly, I was told I can also use snr after between the filtered data and the fft data after carrying out the FFT analysis of the noisy signal

Thanks