At the top you have links to Home - Players - Games. Click games. Then find the game you want to watch live. Right click the "Matchup" button and select "Inspect Element".
Some text should automatically be highlighted, what you want to look for is near the highlighted text. What you want will say something like this:
<div class="twelvecol last" id="players_170644" style="display: none">
What you want to do is copy the numbers that appear after "players_". So in this case it'd be 170644. Then go to a random replay of any old game. And replace the numbers there with the ones you just copied.
Random Old Game:
http://glb2.warriorgeneral.com/game/replay/167700/Becomes New Game To Watch Live:
http://glb2.warriorgeneral.com/game/replay/170644