On the booking page click on the [Add Products] button at the bottom of the Booking Costs panel.
A pop up screen will appear, where you can select the product to add to the booking (you can select a category if you've set this up).
Next add the quantity of the product and click on the [Add] button.
Once the product has been added it will appear in the Bookings Costs panel.
To remove a product from a Booking or if you need to reduce the price of the item. Click on the [Products] link in the left booking menu.
To remove an item from the booking click on the [Delete] button.
To update the price alter the price in the text-box and click on the [Update Prices] button.