First of all you'll need a YouTube account and for that account to be activated to accept a live stream.
To do this once you have a YouTube account, sign in to your account then click on the camera Icon top right of the YouTube home page.
This will then open up the live stream page and it will run through the live stream activation settings for you if it's not already been done.
This gives YouTube some time to check out your 'history' before it allows you to stream to their platform.
Once this is done (normally within 24 hours) go back to the YouTube page and log in, click on the camera icon again and then click 'go live', then click on 'classic live stream' at the bottom right of the screen.
This will take you to the management page of your site, there are plenty of settings on here that you can adjust to your own requirements, however the essential part is the stream key which can be found as you scroll down the page under encoder set up. Click reveal and then copy the key.
Return to PCS pro and go to Tools>Configuration>Live stream and paste the stream key into the stream key box.
If the streaming service box hasn't been populated with YouTube then please select this from the drop down box.
Leave the resolution at 720p for now and the bit rate at 2500. These are the YouTube default values but can be adjusted if needed.
Close that window down and go to the video display in PCS pro (view > video > video display and then click on the 'cog' top right of this window, then select Show Streaming overlay control).
Once there is video in the window and the toss has been done for the game, the start live stream button will appear, click on this and assuming that you have good upload speed on your internet connection then you will be streaming to YouTube.
The Stream button will turn green to reflect this.
Please note: at least 4 MB of dedicated upload speed is required and a laptop / pc capable of handling live stream video.