a With Statement is just one way to access a specific instance of an object.
Example:
with(instance_find_id[box, 1010010]){
// Change variables
widthSprite = 100;
heightSprite = 100;
}
These two variables belong to "box" with an id of 1010010 and no other objects or "box" instance.
However, this statement is written not inside the "box" object but from a controller object or another object.
But thanks anyway for the link