Select the event that you want to delete and select "Delete" (Del) in the "Edit" pull down menu, or click "Delete event(s)" button, which is the "x" icon button on the toolbar. When the confirmation message is shown, select "Yes" to finalize the deletion.
The 'Delete event(s)' button
hint
[HINT] If you delete an audio event by mistake, there is the "Undo" function which enables you to undo once.