In the Blender Preferences, go on the left side to the Add-ons tab and click on the install button on top.

Navigate to the section_view_plane_V1.zip file (do not unzip) and install.

Click the check box to enable the addon.

The addon will be visible in the 3D viewport in the N-panel.

Just reach out to me on Blender Market via the 'Ask a Question button on the right side of the product page.

Thanks