Update README.md

README.md

@@ -27,9 +27,18 @@ Print the tags provided in [apriltags.pdf](apriltags.pdf) and put a tag on each
 Thymio with the corresponding color. The activity is meant to be used with VPL,
 or the automated start won't work.
 
+## Choosing a webcam
+
+The first window opened gives you the ability to choose one of your available
+webcams. The webcam you choose will be used to scan the tags to register the teams
+and to detect when a team has reached the goal. When you are happy with the selected 
+webcam, click the validate button.
+
+![](images/webcam_chooser.png)
+
 ## Register the teams
 
-The first window opened is to register the teams before starting the activity,
+You will then be able to register the teams before starting the activity,
 each team needs to put its name and scan the tag on its Thymio. Then you can
 choose an activity and the time of the activity, and press the start button to show
 the scoreboard.