Navigate to Your Shopify Admin > Settings > Checkout
Scroll down to the Post-purchase page section. Choose UpsellPlus Checkout Offers. Click Save!
That’s it. Once you enable a post-purchase offer in the app, it will appear for your customers.
Shopify has some limitations and considerations for the post-purchase page, you can read about them here.
The main restrictions are that a post-purchase offer won’t work with: