Where do I type the Apple verification code in iTunes on my laptop?

I have been having problems with y itunes not connecting to my phone. So

I removed itunes from my laptop

Installed iTunes 12.1.3 for 32 bit laptop

Phone connects and backs up ok.

Rebooted phone

Rebooted laptop

Checked mobile device driver up to date

Used different cable between phone and laptop.

Message The iPhone could not be synced because the sync session failed to start pops up.

Tried to authorise this computer:

Entered Username and password for Apple ID

Code pops up on my phone

WHERE SHOULD I ENTER THE CODE ON MY LAPTOP? No pop up box appears anywhere.

Driving me nuts!

Please help. Thank you.