Adding a Manage Subscription Button to Shopify's New Customer Accounts page is very simple and requires zero programming experience!
The first step is accessing your theme editor, which you can find under Sales channels → Themes → Customize.
Once you're in your theme editor, click the Icon which shows your current page. By default when you open your theme editor, you'll be on the Home page. After you've done this, click on Checkout and customer accounts.
Now click on the symbol highlighted below on the left hand side of your screen. This is will display a list of all of your installed Shopify apps with an app embed available. If needed scroll until you find Appstle Subscription. Next click on Manage Subscription Button and choose the page where you'd like to show the button - your three options are Profile, Orders, and Order status.
Now that you've selected the page where you'd like to display your Manage Subscription Button (we chose our Profile page), all that's left to do is position the button. You have three choices for alignment: start (left side of page), center (center side of page), or end (right side of page).
If you'd like to adjust where the button appears on the page vertically, you can use the highlighted buttons below to move it up or down.