Uploading files in Cascade is easy, simply navigate to the Goal Hub of the Goal you'd like to attach a file to. Once in the Goal Hub, you'll notice an 'Add Update' button, this is where you'll be able to attach a file.
All the files you upload alongside your Updates, Tasks or Issues will all be stored in the “Files” section of the Goal Hub. Here you will have easy access to all your files relating to that Goal. Note that this is just an overview of all files – they haven’t been removed from the Issues, Updates etc. to which they were attached.