Inside your Revit Architecture application, go to "Add-ins" tab >> "External Tools" panel >> "Level Generator" to start the command. The "Level Generator" dialog appears. The existing levels in the current document are listed in the table with gray color. The gray columns (Index, Elevation) are not editable. To insert multiple levels to the table:

1. Click on the existing level above which you want to add new levels.

2. In the right side of the dialog, "Insert multiple levels to table" area, specify the following:

Prefix - prefix to the level number.

Start Number - starting number of new levels.

Suffix - suffix to the level number.

These three items will define the level names.

Level height - the height between two levels.

Repeat Levels - # of levels you would like to insert.

After you have specified this information, click "<< Insert" button. This fills in the table with the floor information. Note: At this stage, the new levels have not been created in the Revit document. 

The installer that ran when you downloaded this app/plug-in from Autodesk App Store will start installing the app/plug-in. OR, simply double-click the downloaded installer to install the app/plugin.

To uninstall this plug-in, exit the Autodesk product if you are currently running it, simply rerun the installer, and select the "Uninstall" button. OR, click Control Panel > Programs > Programs and Features (Windows 7/8.1/10) and uninstall as you would any other application from your system.