irst: You can do it right from the Webroot's interface - just navigate to the "My Accont Options", then press the "Upgrade / Renew" button and you will be directly redirected to the license renewal form via web browser - just fill it with the necessary data. Probably it's the easiest way:
Second: You can do it from your Webroot Account (if you have been registered user) visiting the adress: and choosing "Buy a Keycode now" or "Upgrade/Renew" option across your actual Keycode
Third: You can simply buy a new license through Webroot Online Shop, enter the new Keycode in the field "Active a new key code" and press Activate button:
https://www.webroot.com/au/en/renewal
I am not sure how much to renew Webroot but you can call too Purchases, renewals, and upgrades
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Tel: https://tel:+18666124268