Sometimes you might find that you've added a file to your project that you no longer want to include.
From the Project Details page, you can scroll down to the Files section and click on it. Once it expands, choose either the Internal or Public tab to show the list of files under that heading. You can then click on the Actions -> Delete to remove the file.
If your file doesn't erase immediately, please try refreshing the page to show the changes made.