Just click the red Add Item button in the header and choose the file option.
You can choose any file to upload (up to 250MB). If you like, you can give this file a name — if no name is provided, we'll just give the item the same name as the file you've chosen.
When you click Upload this File, we'll begin the upload. Please wait for the upload to complete. When the upload is complete you'll be taken to a page where you can immediately choose which, if any, of your contacts you'd like share with and which, if any, folders you'd like to place the file in.
If you know you don't want to share or organize this file, you can check the box for: Add without sharing or organizing and when your upload is complete you'll be taken directly to the item.
Depending on the speed of your Internet connection, it may take several minutes to upload larger files.