How to use blueprint classes as assets?

I have a blueprint class called “Item”, wich is derived from “Object”, and a child class of “Item”, which is called “Sword”.
Now, I want to have an array of Items in another class and a sword instance inside it, but when I try to create it, the sword class is not shown in the drop-down menu. It looks like this:
How do I solve this problem?

You created an array of actor references. So you can only add references to instances of your sword class (meaning you have to spawn them).