Every domain name is tied to a specific IP.
When making DNS changes, you will need to connect the domain name to an A record, or IP value.
Pulse Commerce can handle your site's DNS records, but if you manage your DNS on your own, you may need to know your site's IP.
There are several free 3rd party tools you can use to look up your site's IP and other DNS values.
Here's Google's easy to use DNS lookup tool:
Enter your domain name into the box and select A for DNS type.
You can double-check your site's IP by pasting it into your browser. If your site loads up, that's confirmation that the IP is correctly connected to your site.