Yes you can, as long as you don’t mind your legs being limited in where and how they can move. But there’s no reason why you can’t place books, files, or other easily stackable items that you need into the space underneath your desk. Given that most of these black computer desks aren’t equipped with extra storage, using the space that you have is a good idea. Just be aware that you might need to slip out of your chair and get onto the ground if you want to grab your items and bring them up to your desk. At least you get a workout!