Here's a live shot of using the quad screen feature.
To use the feature, first click on the Live Sports section. Once there, to enable more than 1 viewable screen click on the SingleScren button. This will turn on the MultiScreen feature.
From there, Click on WATCH NOW beside the event you want to view (then pick a source) and you'll see a number get added to the top of your screen, like below. Once you've picked all your streams, up to 4, then click the PLAY button at the top and away you go!