Click on the fibo to select it.
Right click and select 'Fibo properties...'
Select the Fibo levels tab (see attached screenshot)
Then click the Add button, and (to add a -38.2 level, for example)
type -.382 as the Level, and -38.2 = %$ (or whatever you wish) as the Description. Repeat this step to add as many new levels as you wish.
Click the OK button.
You can see the -38.2 level that I added, in the screenshot.
