Adding AttributeSets to your actor
You create attributesets in the constructor:
CreateDefaultSubobject<UMyAttributeSet>("MyAttributeSet");
This should be done in the actor which contains the AbilitySystemComponent. It will automatically gather the attributesets defined in the actor, so you don’t need to manually register them.
You can optionally store the attributeset in a property on your actor if you need it for something, but it’s unnecessary for the ability system component to function.