On the "Media Pack Search" page select "Oracle Business Intelligence" from the first dropdown, and the platform from the second list.
You should get two search results; the second one is the one you need to click on if Siebel Business Analytics 7.8.5.2 is what you are interested in.
You have to agree to some Export validation T&Cs.
Different components are listed in the Media Pack - select some or all as you need.
