Increasing sample rate of ADC on FRDM-KL25Z

Hi Everyone,
I am rather new to Mbed and trying to configure the sample rate of ADC on the FRDM-KL25Z. I am getting one sample for 37us when I connecting 500 Hz sine wave to AnalogIn pin of the board. So, for one period of the wave, I only get approximately 54 sample points. However, I need more samples in that frequency. I’ve searched in the forums but I could not find how I can do it. In the user manuel, I found this:
Resim1
Additionaly, this is my code for understanding the sample time:

#include “mbed.h”
#include <stdio.h>
#include <time.h>
#include <stdlib.h>
Serial pc(USBTX, USBRX); // tx, rx
AnalogIn input(PTB0);
Timer t;
Timer t2;
Timer t3;
int main()
{
pc.baud(115200);
float voltages[100]= {0}, voltage;
t.start();
for(int i=0; i<100; i++) {
voltages[i] = input.read();
}
t.stop();
t2.start();
for(int i=0; i<100; i++) {
pc.printf("%f\n",input.read());
}
t2.stop();
t3.start();
voltage = input.read();
t3.stop();
for (int i = 0; i<100; i++) {
pc.printf("\n%.6f", voltages[i]);
}
pc.printf("\nStoring time: %f\nTime of printing data only: %f\n1 sample: %f\n", t.read(), t2.read(), t3.read());

}
Unfortunately, I did not understand how I can write these configurations in mbed. Thank you in advance.