If you are new to video editing, there's no need to install Sony Vegas or Adobe Premiere - it's better to start with something simpler. I suggest that you get to know the functionality of the free program Shotcut, which is ideal for beginner videomakers. Admittedly, I myself started with Vegas, but 99% of its features I did not need at the time. You can use Shotcut to edit a screencast, a simple YouTube video or an amateur video.