Quite honestly wherever you put them. If you don't know where they are, Koodo and others won't know. Furthermore, this isn't a Koodo issue. Contact either the phone manufacturer or your laptop manufacturer. Koodo provides a service, they don't make the phones and their features.
It depends on where you are downloading them from. For example, if its from a website it should go to downloads, If your downloading them from tumblr then it creates a folder for tumblr downloads, and same goes for facebook, pinterest, etc. If your phone didn't do that then there should be a folder in your apps called my files and they should be in there somewhere :D . hope this helps a little.