Hi Stuart - welcome to the forum ... There are a lot of free and pricey video editing software's that have various degrees of impact on your PC.
As a beginner myself - I'm using 'Wondershare Filmora' -
[OFFICIAL] Wondershare Filmora - Easy, Trendy and Quality Video Editor - which has a lot of on-line help, and allows you to use in a 'free' form until you either decide to use it fully, or dump it. It costs $60 for a lifetime license and makes it easy to produce and edit video, as well as giving you license free music tracks. I've also downloaded a [free] module to it that gives a lot of flexibility in editing all the contrast, brightness, tints, etc. etc. you'd want for post-production.
I was using VSDC Free video editor, but that is really resource intense on my PC, and outputs in large file sizes!