Steps to use Cadsum STL Exporter for Fusion 360:

1. Open your Fusion model in an appropriate Fusion version.
2. Click on the "Export STL" button in the ribbon bar and you will get a dialog with settings options.
3. Now click on the Export button and you will be directed to the save dialog to select save file location.
4. Your exported model will be saved in the selected file location. View your exported model in the appropriate viewer. 

Steps to Activate: 

1. Click on the "Activate License" button in the ribbon bar.
2. Enter the license key and press the Activate button. For license activation, the internet is required.

Install:

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.

Uninstall:

You can unload the add-in without uninstalling it by clicking the "Stop" button when the add-in is selected in the list box on the "Add-Ins" tab of the "Scripts and Add-Ins" dialog.

Unchecking "Run on Startup" causes the add-in not to be loaded in future sessions of Fusion 360.

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, you can uninstall it from 'Control Panel/Programs and Features' (Windows 7/8.1/10), just as you would uninstall any other application from your system.