If you connected an existing domain to your IM Creator site though Google Apps, in order to link your 'naked domain' (yoursite.com, without the "www"), to www.yoursite.com, please add, in your domain registrar's panel, an empty A record (with '@' under Host) that directs to the address: 220.127.116.11.
After you change the record log into your Google Apps account. Go to Domain Settings> Domain names, under 'status' of your primary domain click the link to redirect your naked domain.
Still don't see your site when you type in the domain without "www"? You may be viewing a cached copy of the page - clear your cache and try typing the domain name in the address bar again.
If you connected directly to IM Creator simply add the A record: 18.104.22.168