Start by covering the top screen with a thick plastic or even a wood piece.

monitor keeping rule number 1: NO VENTILATION OPENINGS.

I can see you are raw when it comes to monitor keeping.

I could write a lot of things but I'll start telling you to read this:
http://www.amazon.com/Savannah-Monitor-Lizard-exanthematicus-ebook/dp/B007SF988K/ref=tmm_kin_title_0

And it doesn't matter it's about exanthematicus. They are all pretty much the same.

After you read this, you can start learning.

PS: you chose a difficult and shy species by the way. You'll need lots of patience and HANDS OFF the animal.