1. Create a component in the Design workspace or open a Fusion design that contains a component. 
2. Switch to the "Utilities" Tab, and click on "Make" Button.
3. Select "Print Utility" as the "Preparation Type"
4. Select "Custom" as Application
5. Click on the "Application[None]" folder icon and navigate through "Select from my computer..." to meshmixer.exe (default installation directory: C:\Program Files\Autodesk\Meshmixer)
6. Select the object(s) you want to open in Meshmixer
7. Click OK and Meshmixer opens with the object(s) you selected.

All the Meshmixer usage instructions can be found here:
https://help.autodesk.com/view/MSHMXR/2019/ENU/

The forum with a huge community can be found here:
https://forums.autodesk.com/t5/meshmixer/bd-p/6013

A playlist of how-to videos can be found here:
https://youtube.com/playlist?list=PLu8TYSQ5jCFjdQBHsLoybhdKXOTmpTRlb&si=akhyHrScna2G6sfq

Installation

1. Double-click on the downloaded Autodesk_Meshmixer_v3p5_Win64.exe.
2. Uncheck "Associate STL files with Meshmixer" if you do not want to have this feature
3. Change the installation directory if needed (default: C:\Program Files\Autodesk\Meshmixer)
4. Click on "Accept & Install"

Uninstallation

1. Open "Add or Remove Programs" from Windows
2. Search for "Meshmixer"
3. Click on it and press "Uninstall"
4. Press "Uninstall" in the Meshmixer Uninstaller