Once logged in to Shopify, click on the Apps tab on the left side of the dashboard,

Find the Recharge App (Recurring Billing by Recharge), and click on
the hyperlinked text,

Once redirected, click on the Settings icon on the top right corner,
move down to and click on the Checkout option,

On this page, you will have the option to enable javascript on the 1st page
of the checkout funnel - here is where we'll want to add the Yieldify tag,

Copy the Yieldify tag and paste it into this box. Click Save and you're all set!

We'll also want to do the same with the Thank You page - there's an additional step that you'll need to complete when adding the tag,

Before pasting the tag, add the following statement to the box:

You can now paste the Yieldify tag into the [Yieldify Tag] portion of this statement,

This statement ensures that, if a user reloads the page, we don't track multiple sales - the image below shows what this should look like:

Again, click Save and you're done!

https://support.rechargepayments.com/hc/en-us/articles/360008683434-Adding-additional-content-and-scripts