Glad you inquired about the oven's steam function, Emily!
This wall oven has a Water reservoir that can help you do the steam bake, steam roast, and hybrid clean. For the steam bake and roast, please use the upper oven.
Please refer to this link to your user manual for assistance. Turn to pages 19, 28, 31, 32, and 45 for your reference.
https://downloadcenter.samsung.com/content/UM/201904/20190417153009320/NV51K7770D_AA_DG68-00856A-03_EN-MES-CFR.pdf
Have a great day!
^Chrystel