Please log in to your account and click on "My Domains"
Click on icon, next to your desired domain name
Once you will see the full domain details, please set our "Default name servers" and click on "Save Changes"
Note: once you change the name server, it will take few hours before DNS can populate.
once done above, please click on "DNS Management" button on same page.
Click on "Add a new A Record"
Leave the host name blank and add your IP address in IPV4 address field. TTL: 1000 click on "Add Record"
To create WWW site:
Add "www" in host name and add your IP address in IPV4 address field. TTL: 1000
To create sub domain:
Add "subdomainname" in host name and add your IP address in IPV4 address field. TTL: 1000