Associate ScriptableObject with entity?

I’m using scriptableobjects as a base to create entities in a GameObjectConversionSystem, but there are cases where I need to use GetPrimaryEntity on the scriptableobject.

I see DeclareReferencedAsset, and GetPrimaryEntity has an Object overload, but how do I actually create the entity to be retrieved later?

Trying to use GetPrimaryEntity just warns me “… is an Asset that was not declared for conversion and will be ignored. (Did you forget to declare it using a [UpdateInGroup(typeof(GameObjectDeclareReferencedObjectsGroup)] system?)”

Actually it looks like DeclareReferencedAsset is all I need? Seems to create an entity with Asset too.