This page will take you through how to point your domain to Squarespace. After you connect your domain over at Squarespace (they provide a good tutorial for that process), a new panel will open providing you the records you need to enter into the Advanced DNS Editor at Domain of One’s Own so your domain can be pointed correctly to Squarespace.
For Squarespace you need to create two CNAME Records and four A Records. The CNAME records appear to be used as a way to verify your account. You can see an example below. Keep in mind the Name field for the verify.squarespace.com CNAME will be have a unique code in front of your domain. What is listed below for the Name field will be a value Squarespace will provide.
The second CNAME you create will have www.yourdomain.com in your Name field.
You will then need to add four A Records pointing to four different IP address that Squarespace provides you.
Below is a look at the four A Records created for the example domain.
That should be all you need to get your domain mapped to Squarespace.