login to your redback admin

go to shop > stacks

click add new (or click an existing stack to edit)

fill in details

the price and RRP boxes are not used if your site auto-calculates the stack totals

in the stack-products tab search for a product

you can use the 'options' dropdown in the results to select a specific option

click add to add the product to the stack

repeat for all products in the stack

once all products are added, you can set the options and discounts for the products included in the stack at the top of this area

in the frontend, next to the buy buttons are some dropdown boxes which allow the customer to select which product they require

- eg 'pick from one of these two products and get a free item'

the dropdown for 'option' will change which item is shown by default in the front-end

the dropdown for group will determine which group to show for the user to select between, if the product is in more than one group

the Item Type dropdown determines what to show in the main dropdown for the user

- product and all options will allow a choice between each item from the 'shop > products > product > product options tab'

- selected option only will allow no choice, and will show the item selected in the dropdown for 'option' on the left

- all products in group will allow a selection between everything in the group (shop > products > product > groups >)

discount type can be set to 'none' or discount value (without a percentage symbol)

- none will add the product at its current price to the stack

- discount value will add the product at a reduced price - the percentage discount to add is input in the box below

** Stacks will show as out of stock if any of the items in the stack are out of stock (the back-order functionality is not available in stacks)

for example, to set a stack that allow the customer to pick from one of these two tshirts and get a free red cap you would:

1) goto admin > shop > stacks > add new

2) search for tshirt

3) click add

4) search for cap

5) click add

6) in the dropdown for 'itemtype' for the tshirt product, select 'all products in group'

7) in the dropdown for 'itemtype' for the cap, select 'selected option only'

8) in the dropdown for 'option' for the cap, select the red version

9) in the dropdown for 'discount type' for the cap, select 'discount value'

10) in the 'discount value' box, enter 100

11) click save