If you are a shopify Plus user, you have the ability to edit the checkout.liquid section of your website, allowing you to add in Justuno and any other third party scripts to the checkout page!
Step 1: Contact your Merchant Success Manager, they can turn on the checkout.liquid portion of the site for you.
Step 2: Head to the themes portion of your Shopify platform and hit edit HTML/CSS
Step 3: Hit “add new layout”
Step 4: In the drop down menu, you will find a “checkout” option. Add that file and it will create a checkout.liquid template for you.
Step 5: Scroll to the bottom of that file and paste in the Justuno embed code, here is an article helping you find that!. Justuno will now work on your checkout page!