press the delete key, or
click on the big "X" on the toolbar, or
right click on it and select delete.
I suspect your question arises because you can't seect it without it opening in the preview pane in the bottom part of the screen?
If this is so, to get rid of the preview pane, on the menubar at the top of the screen;
untick the box "show preview pane"
I hope this helps,