Once installed, the "DXF Spline To Polyline" add-in will create a new button in the menu of the "Model" workspace's "Sketch" panel.

When you run the command it will ask you for the number of sections it should divide each spline into.

After that you can provide the path and filename of the DXF file that the sketch geometry will be exported to.

Install:

The installer that ran when you downloaded this app/plug-in from Autodesk App Store has already installed the app/plug-in. OR, simply double-click the MSI to install the app. 

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\Programs and Features' (Windows 7/8.1/10/11), just as you would uninstall any other application from your system.

The source code for this add-in, written in Python, is available inside the add-in's folder or on GitHub

(C) Copyright 2015 by Autodesk, Inc.

Permission to use, copy, modify, and distribute this software in object code form for any purpose and without fee is hereby granted, provided that the above copyright notice appears in all copies and that both that copyright notice and the limited warranty and restricted rights notice below appear in all supporting documentation.

AUTODESK PROVIDES THIS PROGRAM "AS IS" AND WITH ALL FAULTS. AUTODESK SPECIFICALLY DISCLAIMS ANY IMPLIED WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR USE. AUTODESK, INC. DOES NOT WARRANT THAT THE OPERATION OF THE PROGRAM WILL BE UNINTERRUPTED OR ERROR FREE.