This area of the site is dedicated to the rendering of graphics using XNA. Before embarking on this section I would advise you to read the notes in the XNA Getting Started area of this site.
As you saw when implementing a simple triangle in the Triangle notes there is quite a lot you have to do in order to get 3D objects to render. You need to set the projection matrix, world and view matrices. You need to decide on a vertex format and how you wish your vertices to be rendered. This section of the site has more detail on these areas plus rendering 3D models and handling animation.