This page provides some simple tools for video editing.
Windows 10 has a Video Editor application. It should be pre-downloaded in your Windows 10 or is available for free from the Microsoft Store if not. This software is simple but limited. It is useful for trimming videos, cutting out sections from clips, and combining many clips together.
Here is a guide on how to use it from the Academic Continuity Guidance support page: 7. Editing Video in Windows Video Editor
Apple devices have iMovie as an option either installed by default or available via the App Stores.
There are many free open-source editing platforms online for you to download. These have a steeper learning curve than Windows Video Editor and iMovie, but are more sophisticated and allow you to make more complex edits. They all have detailed guidance and tutorials for use.
This is a very powerful option, and has a steeper earning curve than the other options. It is one of the most advanced free editing software platforms but can do very advanced work. It does require an advanced PC to operate however, so may not be the best option for simple editing work.