Once you open the Automation tab and click on "New Automation campaign", you will have to follow the steps described below:
Step 1: Trigger
The trigger event is “Places an order”.
Narrow the selection down with the additional parameters. Select “Product is” and the specific product you’ll be cross-selling/ up-selling.
Step 2: Create the email flow
When cross-selling, your message can be timed for after a day or two.
You’re offering a new item so they might need some time to make a buying decision again. In this case, the discount coupons the email composer offers come in handy.
When up-selling, your message should be sent immediately after they placed an order.
Step 3: Exit
Set the campaign to stop if the customer places another order.