Within the Shopify Admin, go to Settings > Checkout and you will see a card titled Checkout customization. Click on the Customize button to enter the checkout editor:

The Grapevine Surveys app block can be added to both the Thank You page (the initial post-purchase page after checkout) and the Order Status page (the page used to display the order summary at any point after the initial purchase).

You will need to add the Grapevine Surveys app block for each post-purchase page separately, however, the steps you need to take are almost identical for each.

You will see the option to customize the Thank you page or Order status page by clicking on the dropdown in the top bar of the checkout editor:

Let's go ahead and customize the Thank you page first.

Within the checkout editor, click on the dropdown selector at the top of the page and select the Thank you page.

Once the page loads, take a look at the left-hand panel of the checkout editor, locate the Order details section and select the + Add app block link at the bottom of that section:

Grapevine Surveys will then appear as an available app block to be selected:

Click on the Survey Form app block and the checkout editor preview panel will update to show your post-purchase survey on your Thank you page:

Hit the Save button in the top right of the checkout editor.

Within the checkout editor, click on the dropdown selector at the top of the page and select the Order status page.

Once the page loads, take a look at the left-hand panel of the checkout editor, locate the Order status section and select the + Add app block link at the bottom of that section:

Click on the Survey Form app block and the checkout editor preview panel will update to show your post-purchase survey on your Order status page:

Hit the Save button in the top right of the checkout editor.