How can I delete uploaded files

To delete the uploaded files, you'll need to delete the related submissions from your account. As I check your account, I don't see any occupied space with the files in your account. Please be noted that the deleted submissions cannot be recovered in any way. Please make sure that you are having a backup of your submissions/files before you delete the submissions. You may consider integrating Google Drive or DropBox for backup purposes.

Hope this information helps.