how to delete uploaded stuff (to free more space in the account)

Hi there,

To delete uploaded files, you need to delete the submissions with files attached to it. 

Please note that deleting submission data is irreversible and please make sure that you are having a backup of your submissions and files before deleting the submissions.

Here's a guide: https://www.jotform.com/help/377-How-to-Delete-Form-Submission-Data