Make a new, larger array and copy the values of the old one into the new one.
Object[] tempArray = new Object[myArray.length + increment];
for (int i = 0; i < myArray.length; i++)
tempArray[i] = myArray[i];
myArray = tempArray;
Every time you add an element, you should check to see if the array is at its limit, and if it is, call a method that makes it larger.
I do suggest learning the linked list method, however, as they offer much more functionality (such as the logical extension of them, binary search trees).