Many errors in your code.
Try this.

public class e32 {

   public static void main(String[] args) {

   int a = 6;
   int b = 3;
   boolean k =  ( ( a % b ) == 0 || ( b % a ) == 0 );
   boolean i = k;

   // the method isVeelvoud is not needed

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<sscce>
/* ClassNames start with captials, so this should be 'E32', but 'E' should
itself be a word so that would be 'Exercize32'.  OTOH, since we do not care
what exercise this is, you should do a global rename on it to something
sensible just before posting.  I suggest 'TestMethodValueReturn'. */
public class e32 {

   public static void main(String[] args) {

       //  please indent your code consistently with spaces
       int a = 6;
       int b = 3;
       int c = 7;
       // what was this mess suupposed to do?
       //int k =  (a % b == 0 || b % a == 0 );
       
       // the method now returns a boolean..
       boolean modIsZero = isVeelvoud(a,b);
       System.out.println( "a % b == 0? " + modIsZero);

       // ..which we can call with any parameters
       System.out.println( "a % c == 0? " + isVeelvoud(a,c) );    
   }

   /** To clarify that these attributes passed in the constructor
   are not the ones declare above, I changed the names. */
   static boolean isVeelvoud(int firstOperand, int secondOperand) {
       return (firstOperand%secondOperand==0);
   }
}
</sscce>

HTH

   
    k would be boolean here.

You can return boolean values, but your code makes no sense.  k should be a
boolean.  You are calling isVeelvoud with 1 parameter, but takes 2 parameters.
Also in this function, you're comparing "a", an int, to "true", a boolean value.
You need to figure out the logic of your program and clarify exactly what you're
trying to do.