B of the way the mattress is designed, you can't use fitted sheets, and you also can't use a fitted mattress protector / pad, or even a mattress topper.
The problem is there's no way to get underneath the mattress, so you can't tuck anything in there or get to the bottom of it.
The folks who designed this really should have come up with a solution to this problem...just off of the top of my head, why not have it come with a stock mattress protector / fitted sheet combo that is washable and attaches using velcro (hook and loop) strips to each foam section? That would've done the job just fine...
The other problem is that the foam itself isn't good quality.
It's not terribly thick, and it's also not firm enough to maintain its shape when used multiple nights per week by someone who is at least 175 lbs, or heavier. You'll find that it wears out very quickly.
It's nothing like a Casper or equivalent foam mattress, that will last for years and years.
I wouldn't recommend this at all.