1. Open Site Settings at the root of your site collection;

    SiteSettings.PNG

  2. Select Solutions, under Web Design Galleries;

    Solutions.png

  3. Select the already existing web part solution and Deactivate it;

    Deactivate WSP.gif

  4. Once it finishes deactivating, Delete the solution from the gallery.

    Delete WSP.gif

The BindTuning Web Part is now uninstalled from your SharePoint site.