Here is a simple step-by-step guide on how to send a letter:

1. Write Your Letter
   Write the message you want to send on a piece of paper.

2. Choose an Envelope
   Place the letter inside an envelope. Make sure it is the right size and shape.

3. Address the Envelope

   • Write your return address in the top left corner (your full name, street address, city, state, ZIP code).
   • Write the recipient's address in the middle or bottom center of the envelope (recipient's full name, street address, city, state, ZIP code).
   • Print addresses clearly, use capital letters, and do not use commas or periods.
   • Leave space on the top right for the stamp.

4. Affix Postage
   Buy the correct postage stamp for your letter size and weight, and place it in the top right corner.

5. Send the Letter
   You can send your letter by:

   • Placing it in your personal mailbox and raising the flag.
   • Dropping it in a blue collection box.
   • Taking it to the post office and handing it to an employee.
   • If sending internationally or requiring tracking, consider registered mail options.

This is the basic process applicable in the US; the same general process applies in other countries with some local differences. For example, in Germany you can also buy digital stamps via an app, and have specific ways to format addresses and send registered letters for proof of delivery. If you'd like, I can give you specific instructions based on your country. Otherwise, this general guide should help you send a letter properly.