Do I seal the envelop containing my application? Do I need to write anything on the envelop?

Hello everyone! JET Programme Applicant here from Philippines.

Just want to ask (as it was not stated in the application guidelines), do I need to seal the brown envelop containing all my required documents for the application? Do I also need to write something on the brown envelop (ex. Name of Applicant)?

Thank you in advance for the replies!