See previous post for how to select Creative Commons . The Remix Button will appear.
Then you get the YouTube online editor. It has a range of features but it may not be obvious how to use them.
The slider in the bottom right controls the scale of how the clips are shown. Push it to the left to minimise. A hangout, roughly an hour, is too hard to navigate otherwise.
You have to click on the image of the clip for the edges to appear. Then you move the three lines in the middle to select the start and end by moving them. The arrows allow very short movements so get as close as you can before trying them.
This one has been moved from the end so is now 20 minutes, not 60.