To activate KMS Office after purchasing a license, you need to follow these steps: First, install the KMS Office software on your device. During the installation, you’ll be prompted to enter your product key. Input the key you received upon purchase. After entering the key, your software should automatically connect to the KMS server for activation. If successful, you’ll receive a confirmation message, and your KMS Office will be fully functional. If you encounter any issues, you can refer to the KMS support documentation for troubleshooting steps.