Dragging and dropping from Finder.

Hi all.

I'm trying to drop files on to an app, specifically this free sampler, in case anybody wants to try it.

https://audiomodern.com/soundbox/

They say there's a way to do it from the menu, but I don't see an import option in the menu. Also, copy and paste doesn't work, I've tried that already, unless I'm doing it wrong. Here's what I'm doing:

1. Unzip a free instrument.
2. Go into the folder in Finder, get to the soundpack file.
3. Interact twice.
4. Vo-right to the actual file.
5. Hit Vo-comma, it says it's marked for dragging.
6. Cmd-tab to either the standalone app window, or the plugin window in Logic, both do the same thing.
7. Hit Vo-period to drop. It says the item is no longer in view.

IIRC you also have to import some things into Pianoteq this way, which I'm planning on buying soon. SO a way to solve this would be awesome. I don't know if there are any tricks I need to do like resizing windows or something, and if there are I don't know how to do them, I know next to nothing about manipulating windows on the Mac, since it seems largely like a visual thing I didn't need to know about until now, maybe.

If anybody knows the secret, I'd really appreciate your wisdom. Thanks in advance for any help.