For adding an Equipment object, create an addEquipment( Equipment equipment ) method that is called on the backpack instance:
backpack.addEquipment( crowbar );
The class Equipment name should be capitalized as you've done, but the instances of Equipment, the Equipment objects created, should have names that being with lowercase letters:
Equipment crowbar = new Equipment("Crowbar", 5);
is named crowbar, the name
of the crowbar object is "Crowbar". It's important to keep these details straight and to be consistent.
As for listing all equipment added to the pack, since theEquipment is an array of Equipment objects, you can simply iterate the array to print all of its elements using a for or enhanced for loop, similar to what you have but inside a loop and printing each element in turn.