Are you talking about other Fusion components? Like, when you're loading a multiple of them into a single assembly file? Or maybe items downloaded from the McMaster-Carr catalog?
Those should all load into the assembly file, by default, with their origins on the main origin of the assembly file. Problems such as you describe can occur, for example, if you modeled a component way off of its own origin. As you might imagine, when you then load it into an assembly file, its geometry might be located way off in space somewhere. Make sure the visibility (lightbulb icon) is turned on in your Browser (for the component itself AND for the body or bodies nested inside of it), and then zoom way out or do a Zoom All.
Corrective actions may include:
1. Correcting the component file such that its geometry is located on its origin and try again.
2. You're going to use Joints to properly locate each imported component within the assembly file, and that will work even if the geometry is far out in space somewhere. It's sloppy, but it will pull the components into place anyway.
