Sketchfab makes it easy to embed your 3D models right into a Unity Forums post.
You'll want to begin (if you haven't already) by uploading your model to your Sketchfab account. Not only do we support direct export of assets from Unity with our Unity to Sketchfab Exporter, we also support direct file export from the most popular modeling tools in the industry.
Once you've uploaded your model to Sketchfab, you can copy the URL of your Sketchfab model page and click the “Media” icon (two film strips) and enter the model URL (shown below). Once you do that, click “Embed”.