If you have already used a code, you can find it under the "Subscriptions" section on My Kaspersky 2. How to Activate Your Product (Standard, Plus, Premium)
Run the installer. It will download the full 200MB+ database. Once complete, the main dashboard opens.
The primary reason to use Kaspersky is to protect your data from malware. However, websites offering free activation codes are major hubs for malware distribution