Make the view you want to work with active and then hit F6. This will show the camera and target pyramid in the other views and you can manipulate it simply by moving its control points around. The results will show in the view you initially made active. Hit F6 again to hid the camera.
A view is defined by the camera position, the target position and a viewing angle (corresponding to a lens length). You can access these settings in the viewport right click menu, and "Viewport Properties" (or type _ViewportProperties). In the dialog, you can either enter specific coordinates for the camera and target, or you can pick points in the the scene. If you want to do this on the command line, use the dash version -_ViewportProperties>_CameraTarget.
Are you wanting to set the camera/target to specific coordinates for some purpose or rather just to store specific views for later re-use? If you are just looking to store a specific view or series of views, you don't need to deal with camera/target coordinates. Just set up the view you want in a viewport, then in the viewport right click menu, choose Set view>Named views (or type the command _NamedView). In the dialog, hit the Save button and give your view a name.
The next time you pull down the set view menu, you will find your new view name in there, clicking on that will bring back the view. You can also manage views within the NamedView dialog, there you will see thumbnails of all your stored views.