Thunkables File Section

I am trying to add a sound effect onto my app, but thunkable requires me to add in into its file section, but i dont know where that is, and when i search for it it just directs me back to this article, please help

When you add the Sound component on the Design screen tab, click on that component and then upload a file by clicking on the “No file source” field under the Source header:

And after you upload any files, they will be listed in the Files section of the Design tab, below the list of Screens and components: