All widgets are found in the same place on every wordpress.com blog > Appearance > Widgets. All widgets are installed the same way – one at a time by drag and drop.
Drag the widget you want out of the Available widgets box and drop it into the sidebar in the position your want it to be in. Click the top right hand corner and the widget will open so you can configure it. Then click “Save” and “Close”. Then do the next widget until you have done them all.