Hi,
You could upload the files to a folder under /Data/Sites/[SiteID] and then link to them from an Html content instance, the link toolbar item in th editor should let you browse to the files if you upload them under that folder.
That is fine if the files have no security requirements but if you want to protect the files and also have counts of th edownloads you could use the Shared Files feature, which allows you to upload the files directly from your web browser.
Hope that helps,
Joe