REMINDER ALERT !! It is important to add app blocks to both pages (Order Status and Thank You), otherwise it won't work properly.

Video Tutorial: How to add App Block

Tutorial: How to add App Block

From your Shopify admin, go to Settings > Checkout.
In the Configurations section, click Customize next to the checkout configuration that you want to customize.
In the checkout and accounts editor, select the Thank you page and then click the sections icon to access the Sections sidebar.
Click ⊕ Add app block.
In the Apps available for this page section, click on the Packeta - Selection app. The app is automatically placed in the recommended area on the page.
Click Save.
Repeat the step 3.-6. for the Order Status page. It is important to add app blocks to both pages.
Click Publish If you do not have the new functionality already activated.