streamable.com/fszkr
You need to create an instance of an object before you edit the instance's properties.
And how do I do that? (Also, why is it necessary?)
It's necessary because you can't edit the properties of something that doesn't exist. I suggest trying the Beginner's guide to Construct 3 to learn the basics of creating and editing objects.
Develop games in your browser. Powerful, performant & highly capable.
How do I select an instance?