Once you have obtained the installer from the official source, follow these steps:
Step 1: Download the Installer
Step 2: Run the Installer
Step 3: Installation Location
Step 4: Asset Library Download
Step 5: Activation
Do not download Lumion Pro from unofficial "free" sources. If cost is a concern: Lumion Pro 10 2020 Free Download
ActiVision offers a fully functional 14-day free trial of Lumion Pro. This is the only legitimate "free download."