Edit In An External Editor
The software will work in conjunction with an external sound editor in order to apply permanent changes or edits to the sound.  For example, if you want to reverse a sound or edit out clicks and pop or some other audio editing, you may want to use an external editor.  (This requires that you own or have downloaded a sound editor.)

Configure An External Sound Editor
Go to the preferences and choose the General tab to select an external sound editor to use.

How To Edit A Sound In An External Editor
Right click on a sound and choose Edit In External Editor or choose Edit In External Editor from the Sound menu.  You will have the option of editing the original sound or a copy.  If you edit the original sound, the change will be a permanent and will not be undo-able.