NOL works the same way no matter what the business source is. First, after you determine that you have an eligible loss in your S-Corp (because a deductible loss CANNOT exceed your actual basis in the corporation), you would determine your Net Operating Loss carryback amount.
THe NOL amount is computed on Form 1045, Schedule A.
Just because the S-Corp has a loss, does NOT mean you have an NOL.
The allowable S-Corp loss must then be greater than all your other positive income.
Unless you make an election otherwise, the loss amount calculated on Schedule A is carried back TWO tax years. You fill out Form 1045 to show the effect. Any remaining loss can be carried to the next tax year. If an amount still exists, then it skips the current year (because it is alreadyd in there) and goes forward to the next year.
If your S-Corp loss is greater than your basis (the amount you actually invested), then the loss remains unusable until you either have a gain to offset some of the loss or you increase your basis.