The add-in is located in the design workspace under the 'Create' tab. Click the "Polyhedron Generator" button to launch the command.

A popup will appear with dropdown menus. First select a polyhedra grouping from the dropdown menu labeled "Polyhedron Group", then select a specific shape from the dropdown labeled "Select Polyhedron". Click OK to build the polyhedron.

Alternatively, you can use a weblink to access hundreds of more polyhedra. To use this option, instead of selecting from the dropdown menus, click the "Custom Weblink" checkbox. Then input the full URL address to polyhedron shape in the "Link" input box and click OK. To browse for these additional polyhedra shapes, visit http://dmccooey.com/polyhedra/

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 Autodesk® 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), just as you would uninstall any other application from your system.

The polyhedra shape information are distributed here with permission from David I. McCooey (http://dmccooey.com/polyhedra/). Additional references for each shape can be found under their respective page on the polyhedra site.

Polyhedra with self intersecting faces or a large number of faces can cause performance issues during the boundary fill operation. Generally, Fusion will complete the operation with a little time, but some polyhedra with self intersecting faces will fail to compute. When this happens, the faces of the polyhedron should be left as individual surface bodies with visibility off.