Once you have loaded up the training course, follow these steps:

1. Type into the console, record [file name]
2. Once the recording has started, you need to restart the map with, mp_restartgame 1 This must be done otherwise the demo will not playback correctly.
3. Once you're done recording, type into the console, stop Now your demo has been saved.

You can playback your demo by pressing, "Shift+F2", which will open the demo playback menu. Press Load... and scroll down to find the demo you have just recorded. Or alternatively, type into the console, playdemo [file name].

If you want to find where your demo is saved on your computer go to the drive you have installed Steam onto and go: Steam\steamapps\common\Counter-Strike Global Offensive\csgo The file you want will be a .dem file, now you can upload this for others to download and view.