Squarespace uses this format for RSS feeds within your site:

http://SITENAME.squarespace.com/PAGEURL?format=rss

Clicking the link will open a page with your RSS URL that can be copied and pasted into an RSS feed reader. For example, here's my RSS URL to paste into your reader:

http://dl-rss.squarespace.com/blog?format=rss

Subscribe to my RSS here.