How can I empty my upload space?

You need to delete the actual submissions that has attached files or uploaded files. Here's a guide on how to delete your submissions:

1. Select the form then click the Submissions.

2. In the Submission page, you can delete a single submission or delete all submissions.

Note: Deleted submissions are not recoverable. I suggest to download them before deleting them.

Complete guide: https://www.jotform.com/help/377-How-to-Delete-Form-Submission-Data

Hope that helps. Let us know if you need further assistance. Thank you.