First, track your spending and expenses for the next 30 days. You can begin by recording all your purchases on a weekly expense report worksheet that you fill out each day. Save your receipts from each purchase and then record a description of the purchase, the amount, its category, and how you made the purchase; whether by cash, check, or credit card.
The big advantage of cash envelopes is that, if you budget properly, you will always have the cash to pay a bill when it comes due. No more worrying about where the money will come from, be it for mortgage or rent, utilities, car payments, repairs, taxes, discretionary spending, etc.