Moving average and smooth the signals

Hi all,

I am dealing with my homework.

In the guide image, after plot square filtered signals, how can I classify the test data and identify those data in individual trials?

Really appreciate for your help

clc;
close all;
clear;
load('ECG_Biometric_Test_Rand.mat');
load('ECG_Biometric_Train.mat');
Fs = 200;
F_nyquist = Fs/2;
ecg1 = ecg_test_rand;
ecg_t1 = ecg(:,12);
N = length(ecg_t1);
N_half = ceil(N/2);
num_bins = [0: N-1];
ecg_spectrum = abs(fft(ecg_t1));
freq_response = num_bins*Fs/N;
plot(freq_response(1:N_half),ecg_spectrum(1:N_half));
[b, a] = butter(3, [0.01 0.2],"bandpass");
h = filter(b,a,ecg);
plot(h.^2)