- Download the latest version.
- Goto Blender
User Preferences
from theFile
menu. - Switch to the
Add-ons
tab. - Click the
Install from File...
button at the bottom. - Select the zip file. Do not expand. Blender does that.
- Switch to the new Category now added,
Babylon.JS
- Enable the exporter using the checkbox.
- Click
Save User Settings
if you wish it enabled every session.
See the exporters documentation for a list of features, some tips and others.
Tower of Babel extension can be found here.