Go to http://dcc.godaddy.com, enter your username, password and click the Login button.
Click the Manage button next to the domain you want edit.
Click the Launch link in the DNS Manager area of the Domain Details page.
In the Zone File Editor page, click the Quick Add butoon under the A (Host) section. And insert following:
Host: @
Points to: 198.199.88.101
Make sure there is not other A record.
After a few minutes, you'll see the new A record appear under the DNS Manager settings displayed on Domain Details page. That's it. The changes to the DNS servers may take 24 to 48 hours to propogate through the internet, though normally the changes are evident in a matter of minutes.
This video is done by someone else but might be helpfull to see how to edit A record in GoDaddy admin.