I wanted to post more detailed guidance on how to extract these files with 7-zip in case there are more like me that had trouble figuring it out. After you've downloaded IS0_GTPCAMS.7Z.001, 2, 3, AND 4 to the same location (I suggest just making a new folder), you need to use 7-zip to merge these four files. In the folder you created select (highlight) all four files and right click on them. Select "7-zip" and then "extract to "*\"". After 7-zip finishes merging these files , open the ISO_GTPCAMS folder and move the Gamedata and Series folder to your Automobilista directory.