Like @Jared said, you can exchange your crypto in the app’s exchange (pDEX) for a supported cryptocurrency of your choosing. To exchange it for cash, you then send that currency to a different exchange, such as binance, coinbase, etc, and sell it for fiat (cash), which is then transferred to your bank account.
There are a few reasons why you can’t currently sell to fiat from the pDEX, but one of the primary ones is that in the US, an exchange like that requires KYC, which defeats the purpose of Incognito’s privacy. So, you can use the pDEX for privacy and PRV, and if you need to cash out, it’s a simple and easy process to transfer it to a different exchange. Hope that helps!