Installation procedure: Run the "i-model plugin for Revit. msi" installer Click "Next"
Accept the End-User License Agreement and click "Next"
For the required Revit Plugin files accept or change the installation path and click "Next". This will then display the Revit installations detected by the installer.
Expand the "Select Revit installations" item so see which Revit products the installer has detected.
You can now chose for which ones you want the Revit Plugin to be configure. When you have made your choices click "Install" to begin the installation.
See also http://communities.bentley.com/products/building/building_analysis___design/w/building_analysis_and_design__wiki/imodel-plugin-for-revit-overview.aspx