well, casting is basically a promise to the engine. The engine isn’t sure what you’ve spawned with that SpawnActor node. That’s because you feed a dynamic “Class” into it. So casting afterwards says: “Hey…check if you just spawned this kind of actor. If so, we can use specific things in that class.”.
So, what blueprint class of yours has that arrow component that you need? That’s what you need to tell the engine it is. You usually, but not always, want it RIGHT after the spawn. So drag off of the arrow pointing out from the spawn actor node and type “Cast to” in the search bar. Now you’ll need to scroll down to the class you want.
Actually, looking at your first post…its a little tough to tell what you’re going for though or what your experience level is–since “arrow component” isn’t something you can spawn directly (components are…well…components of actors.,.and aren’t actors themselves). You can spawn blueprints that HAVE arrow components in them though…so that might be where your problem is. Create a new blueprint with an arrow component and try and spawn that instead. Depending on how you do it you might not even need to do any casting.