diff --git a/README.md b/README.md
index e9368b2..4a2c960 100644
--- a/README.md
+++ b/README.md
@@ -27,6 +27,23 @@ TODO: need to make this extension gecko-compatible.
 
 ## Usage
 
-Once you have installed the extension in your favorite browser, click again on the puzzle icon in your toolbar to open it (you can also pin it so that it appear in the toolbar).
+Once you have installed the extension in your favorite browser, click again on the puzzle icon in your toolbar to open it (you can also pin it so that it appears in the toolbar).
 
-That's it!
+From the extension popup, you should be able to start a contest, end it, and reset all saved data.
+
+When in a Google Meet tab, once a contest is started, all new messages with be automatically prepended by the time since start of the contest.
+Those messages will also be saved in the `messages` section of the extension popup (so that they are kept in case you close the Google Meet tab by mistake).
+
+## How it works
+
+The extension will look for new messages in the Google Meet messages section, if opened, and assign times to them as soon as they appear there.
+
+If you close the message section, the extension will still be able to log the times of incoming messages because they are appearing in notifications in the bottom right corner of the screen, but it won't actually assign them to messages and save them until you re-open the messages section.
+
+Best is to keep that section open all along though if possible.
+
+## Word of caution
+
+Please note this work is technically dependent on the structure of Google Meet pages, if Google decides to completely rework them, the extension may break in unexpected ways.
+
+However, Google Meet is a quite stable product, and such changes are very rare. So if you check things work nicely the day before your contest, or ideally a few hours right before, then it should be alright!