If you want to redirect your feed from Squarespace to RSS.com just follow these steps:
1. Log into your Squarespace account.
2. Click settings
3. Scroll to the bottom of the page and select "Advanced"
4. Look for "URL Mappings"
5. In the mapping box write your squarespace feed first, leave a blank space, write the symbol ->, leave a blank space and then paste your RSS.com feed. At the end write the code 302 as seen in the example:
6. Your redirect is ready!