illuminate

Do you use this verb as to make something clearer, apprehensible, with more information...

If yes, can you tell me if I used this verb in the right way:

Context: I was trying to read a letter, but some of the words were unclear. I asked someones' help. Her name is Berta. I want to say:

I hope Berta will illuminate on this letter (or on things that were written in this letter).

I don't know how to write it and hope you can help me here. Thank you.

If you do, it should be transitive:

"I hope Berta will illuminate me..."

For the context I gave you, why not:
I hope Berta will illuminate this letter.

To illuminate the letter would be either to literally shine light on it or to decorate it with illustrations, as in an illuminated manuscript.

"Illuminate" works in the same way that "enlighten" does, and is very similar in imagery. You wouldn't say, "enlighten the agreement". You would say, "enlighten me regarding this agreement". You don't bring the agreement or the letter to a new place of understanding/enlightenment/illumination. You bring the person to a new place of understanding/enlightenment/illumination regarding the agreement or the letter.