Save this file, replace the italic grey placeholders with your own words, rename it with your assigned entry number in the form TY0014.html (the TY prefix plus a four-digit number), and submit it via the Submit page. The editor will check it, inscribe it, and add it to the archive.
Keep it specific. Keep it real. As long as it needs to be, with no padding.
[What happened. Where you were. What they did. Enough that a stranger reading this in fifty years can picture it.]
[What it meant. Not what you would say in a card. What you would say to them now, if you could. Why it mattered. What you have done since because of it.]
[An optional closing line. "Thank you, all these years late." Or just "Thank you."]