If you decided to restore your new iPhone from a backup of an older iPhone, you should have already clicked "continue." Once you click continue, you'll see a message on your computer's screen that iTunes is restoring your iPhone from backup. Your iPhone screen will say "Restore in Progress."
This process can take several minutes. Do not disconnect your iPhone or close iTunes while this process is running.
When the restoration is complete, but before your music is synced with the new iPhone, you'll see a message asking if you'd like to share diagnostic information with Apple. This is voluntary; read the disclosure and decide whether you'd like to share this information. Click "Continue."