Here is how to add a PicSnippet to your Shopify order summary page:

1) When generating your PicSnippets code, select 'Shopify Order Summary' as your platform

2) Match your PicSnippet variable with the appropriate Shopify field(s)

3) Copy the code in the HTML box 

4) From your Shopify admin dashboard, go to Settings -> Checkout

5) In the Order Processing section you will see a place to add 'Additional Scripts'

6) Paste in the HTML code you copied from PicSnippets into the 'Additional Scripts' box

7) Scroll down and click 'Save'

That's it! Your PicSnippet will now be added to your Order Summary screen and personalized for each customer :)