[Newbies] how to delete imported graphics

[Ken G. Brown]

This is latest trunk on Mac Squeak 64-32 5.3b1.app

I've done a couple of file list/import of jpgs.
I'm wondering where the jpg's are stored and how do I delete them?
I can see them from World Menu/help/graphical imports but the menubar menu there does not work.

And what is the magic incantation to apply one of them to be the background of the Squeak window? 

Thx for any insight,
Ken G. Brown