The mentioned downloads are included in the autoupdater - no need to download and install them again.
It's just a list, as is "latest cars" and "latest tracks".
All cars, tracks, car-classes, uninstalls, mods are handeled by the autoupdater. Sometimes, when something went wrong, one could try to download the file "per hand" from the list and install it directly, but normally there is no need to do so.
Nevertheless there are downloads to be found, which are not coming with the autoupdater, such as new engine-sounds for some cars or templates for painting a new skin or maps of some tracks, etc. Just follow the link called "downloads" on the left field of this page...
Or directly:
*sounds*
*templates*
*documents*
*mix*