If you currently have an active subscription to PlaceMaker, you simply need to download and install version 3 and then re-activate your license using your email and license key. Use the same license key that you received after purchasing your subscription. If you have lost your key, please go here to have it resent.
If your subscription has expired, you can still upgrade to v3 using the same steps above. However, your license will behave like a PlaceMaker Pay-As-You-Go license and imports will cost more credits than if you had an active subscription. To enjoy the benefits of being a PlaceMaker subscriber again, just renew your license.