There can be 3 reasons why you see boards from others coming up.
1. When you logged on you were automaticly added to watch and listen to the ongoing broadcast of an event.
A: You can close the live broadcast (audio and board) by going to Links list on the left. Click on Broadcast. When the broadcast window opens you can click on the icon above the broadcast named 'Stop following broadcast'
If you are having problems with doing the above steps then go to your Console, as shown below, and type there 'tell webcast nofollow'.
2. You clicked on a follow option for a certain player or type of game.
A: Above the board you should have an icon named 'Stop watching games'.
You can also get this option by going to the Menu above, click on 'Game' and choose 'Stop Watching Games'.
You can also use the 'unfollow' command on the command bar of your Console.
To get your console up click on the Console icon on the bottom (left) of your interface.
Or go to the Menu above, click on 'View' and choose 'Console'.
Now your Console comes up. Here you can type 'unfollow'.
3. You typed or clicked a follow command for Simulbot.
A: Go to your Console and type there on the command bar 'tell simulbot unfollow' (for Console picture see above).
For more information on follow and unfollow you can read the ICC helpfile "help follow" .