How to setup my website on www without redirecting root through Squarespace?

Squarespace wizard does not seem to let me configure www. It asks for root A records for the website. It worked fine for our staging subdomain (staging.explor.ai). When I setup www.explor.ai as the domain, seems like it actually tries to configure explor.ai (the root). I don't want to change the root. What's the work around?