C Functions how do i put this in a function

[Fyrewynd]

Ive been told to put the following code into a function and yet when i try since it is 3 arrays i cant get it to work at all. Any ideas to get me started on this?
I tried using a function like this

void funct1(int x[], y[], z[]);
{
for (i=0; i<funct1; i++)
return      x[i] = i;
return       y[i] = i;
return       z[i] = i;
}

#include <stdio.h>
#include <stdlib.h>

int main()
{
   int x[10], y[15], z[20];
   int i, sumx, sumy, sumz;

   for (i=0; i<10; i++)
      x[i] = i;

   for (i=0; i<15; i++)
      y[i] = i;

   for (i=0; i<20; i++)
      z[i] = i;

   sumx = 0;
   for (i=0; i<10; i++)
      sumx = sumx + x[i];

   sumy = 0;
   for (i=0; i<15; i++)
      sumy= sumy + y[i];

   sumz = 0;
   for (i=0; i<20; i++)
      sumz = sumz + z[i];

   printf ("The sum of the x array = %d\n", sumx);
   printf ("The sum of the y array = %d\n", sumy);
   printf ("The sum of the z array = %d\n", sumz);

   system("PAUSE");
   return 0;
}

It works fine with no function but im told a function would make it easier to read and faster to process although it seems pretty fast to me.

I'm new to C and working through a workbook and don't understand functions real well yet.

Thank you for any assistance.