First, select wall type, then select the base ceiling to be considered its boundaries. You have three options, inner boundary of the selected ceiling, outer, or both of them. 
If you need to create a wall for lightings, then specify its height and select the ceiling boundary to light the walls on it. After that just specify the location line of the walls.

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.