A self-addressed stamped envelope is an envelope with the sender's name and address on it, plus affixed paid postage, that is mailed to a company or private individual.
How to Send SASE manually?
Address the envelope with your address in the FROM section and the company's address where you want to send the SASE to, in the TO section.
Address the envelope with company's address in the FROM section and your address in the TO section.
Drop envelope #1 in post office