To open the extension, go to the "SOLID" section. You can either click on the following icon in the toolbar or click on the link in the "Edit" menu. 

Begin by selecting two solids, ensuring the face in contact with the first plank is fully contained within the face of the second plank.

Then tailor your design using the following configuration parameters:

• Number of Dowels in Length: Set the number of dowels along the length of the assembly.
• Number of Dowels in Width: Specify the number of dowels along the width of the assembly.
• Dowel Type: Choose from round or flat dowels.
• Dowel: Select from a list of standard dimensions or enter custom dimensions for a personalized fit.
• Rotation: Adjust the orientation of flat dowels if needed.
• Width Gap: Set the assembly clearance on each side of the flat dowels.
• Solid Names for Dowels: Define the names for the dowel solids.
• Appearance: Customize the appearance of the dowels from a dropdown list.

If you want to preview the result before finalizing, check the "Preview Result" box. Once satisfied, click "OK" to automatically generate the assembly. 

For more details about the app refer to: https://woodsoul.fr/faddins/dowel-pro/mac

Install:

1. Download the installer from the Autodesk App Store.
2. Right-click on the "Downloads" folder and select "Open in Finder".
3. Right-click on the "DowelPro_macos.pkg" -> "Open With" -> "Installer". 

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®.

- Navigate to the ./ApplicationsPlugins folder and select the app bundle you want to uninstall

- Either drag the app bundle to the Trash or right-click and select “Move to Trash”

- Right-click on the Trash-Can and select “Empty Trash”

- If you prefer keystrokes, you can also just select the app bundle and then hit Command+Delete to move the app to Trash, then empty the Trash and the app will be removed.