[Step 1 | Setup Heroku]

1. Go to Heroku app -> "Settings" -> "SSL Certificates" -> "Configure SSL" -> select "Automatic Certificate Management (ACM) -> "Next".

2. "Domains" -> "Add domain" -> enter your domain (ex: "google.com") -> "Next".

3. Copy "DNS Target" -> "Back to domains".

[Step 2 | Setup DNS]

1. Go to Squarespace Domains -> "Domains" -> select target domain -> "DNS" -> "Custom records" -> "ADD RECEOD".

2. Enter "@" for "HOST" -> select "ALIAS" for "TYPE" -> paste DNS Target for "DATA" -> "SAVE".

3. Back to Heroku -> "Settings" -> "Domains" -> "Refresh ACM Status" (this may take some time).

• For "www.xxx.com" domain check this video: https://youtu.be/ZP7GpxMlxOI