Only an admin or a user with editor permissions can delete an application.
Delete a user-made/downloaded app from the Library
Choose the Application you want to delete. By accessing the three dotted menuyou will be able to select the Delete option from the drop down list.
Note that after clicking on the Delete button your app will be removed from the Apps page, but it will not be fully removed, just archived. At any moment you can ask your Platform Administrator to re-activate it.