You have to map your existing .com
domain to your .squarespace.com
site using the instruction provided here.
The instructions also have domain registrar specific instructions at the end for the following registrars.
You can click to view our guides for mapping your domain if it is hosted with a specific domain provider below.
Dotster
Dreamhost
easyDNS
Enom
GoDaddy
Hover.com
IWantMyName.com
Namecheap
Nettica
Network Solutions
1&1