DynamicArray add element

Hi everyone,
i’m new to Algorand and i’m having some difficulties on Boxes and Arrays. I need to store an array into a box and, when asked, to add an element to that array. The array element type is a custom class i created.
The main problem is that i can’t find a way to add the element once i retrieve the array from the box

Can you show the Array custom class you used?

The array type isn’t custom, i used DynamicArray. However the elements in the array are custom type. The problem is that i can’t find a way to add an element to the array, even if the element type is a base type.
For example, there is not .add() method and the .set() method doesn’t work that way