zen cart questions

i have some questions about zencart and had been surfing (actually suffring) around their tutorial site but have not found or been able to understand the answers and was hoping that any one here might be able to help.

how to setup a file to download after purchase. meaning to setup digital contents. any step by step tutorial.
and also how to setup that if user downloads one file he is able to download another file (as part of a pormotion or something like that) automaticly
and can it be added later manualy.

Install the latest version and during the install select the demo products - there are many, many things that this will answer as the descriptions for the products are like a tutorial along with being able to see the admin settings for these items. BTW the down load is one of the items that is there.