If you are changing the SI screen or cleaning it's upper surface, it has a tab similar to the focus screen.
Carefully lift out the screen and set it aside in a clean area such as a small ziploc bag.
Do not touch the screen with your fingers as any oil will need to be washed off.
Be careful with the tweezers as the screen is easily scratched.

You do not need to remove the SI screen if you are just changing or cleaning the focus screen.