Easy! Log in to your Sloto'Cash account, hit the big red “Cashier” button in the top left of the screen and then choose the “Deposit” tab from the pop up window. On the right hand side of the page, you’ll see the option to choose a coupon. You can use the menu to select “use another code”, at which point you can enter the bonus code, check the box for “redeem on deposit” and then make your real money deposit accordingly.