After Successfully activating any one of the Niche Addon plugins you will get all the widgets of NicheAddons Elementor Addon in the Elementor Sidebar Widget Panel itself by Edit With Elementor Option. Scroll down in the sidebar widget you will find the Niche Addons Widgets.
You can simply drag and drop any widgets from the Elementor sidebar menu like Elementor Widgets. Each widget have the “Content“, “Style” and “Advanced” tab for element-specific and advanced customization options.
