You can sync contacts via iTunes. On Windows it will sync contacts with Outlook and maybe other apps between the PC and the iPhone/iPad. On OSX it will sync from the Address Book/Contacts app on OSX to the iPhone/iPad.

But you really want to sync your contacts via iCloud unless you have a very good reason not to. That way you will have them synced between the iPhone, iPad, your PC/Mac and iCloud.com (for a web UI). If you now have the contacts on the phone it is as easy as adding an iCloud account and letting it merge the contacts on the phone with iCloud.