How do i enter prior year's unallowed losses on an 8582 form for rental prop? My cpa did that last year and not sure how to do that on turbo tax.

You can enter it manually. When you are in the rental section, you will encounter a screen that asks if "Any of these Situations Apply to You". One of the options is that you had prior passive losses. When you click that, you will encounter at some point in the rental interview, the screen shot below.