In your profile in the Settings section, you have the option of resetting your data. To do this, click on the "Delete account" button. You have to confirm twice that you really want to delete your profile and your data, as Well deletes all your documents and data and this cannot be undone. 

In the privacy policy you will find further information on how Well saves, protects and deletes your data. You can find the document in your profile in the Help and Legal section.