Finally got around to testing this deal. Subscription covers turn-by-turn navigation, traffic and speed camera functions.
1) launch OP link. Stay in the German site ie don’t change over to Australian / NZ site as promo code won’t work. No VPN required.
2) sign up or log in using an existing account. If you’re signing up, you’ll need a German address. If you’re using existing account, you’ll need to migrate your account over to Germany to get the free 12 month extension.
3) download the TomTom Go app to your phone. Sign-in to 'TomTom Services' via 'Settings' to confirm subscription for 1 year.