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[If these weren't mail-related questions, she might be a little more irritated. But she chalks the pause up to secret embarrassment.]
Ah! It's simple, really. You may stop by the convenience store or the post office to acquire stationery and envelopes. Write your letter, address your envelope--there are diagrams at the post office, but if you don't stop by, you write your address in small lettering in the top left corner, and the recipient's address in the middle in a more normal lettering size. Seal the letter inside the envelope using its tongue-activated adhesive, and and either tuck it into your mailbox with the flag up- [Pointing to it.] -or leave it in the drop box at the post office. Whichever is most convenient for you!