I want to open an account in apple. From where i start?

What exactly do you want to do ? As you've posted here you have an iTunes account (or Apple id, they are different ways of referring to the same thing) and you can use it in the stores (iTunes, App Store, iBookstore, Mac App Store) to download items. You can log into the account on your computer's iTunes via the Store > Sign In menu option

On an iOS device you can log in via Settings > iTunes & App Store

Where you can use your account : Where can I use my Apple ID? - Apple Support

Apple ID FAQ : Frequently asked questions about Apple ID - Apple Support

Apple ID support links : http://www.apple.com/support/appleid/