Basically, you just need to follow the instructions in the YouTube video below. It is very easy and fast. The key software is VirtualBox.
You can download the official Windows 10 ISO disc image here: https://www.microsoft.com/en-gb/software-download/windows10ISO
Note that Windows 10 (Home) is free (you don’t have to activate it) and you can use it with only very minor restrictions.
Overall, the process to install Windows 10 on a Mac (using VirtualBox) is much easier than I expected.
Total time taken: Around 30-40 minutes (possibly faster if your download speed and RAM is fast)
Total cost: $0
Total space needed: Around 10-20 GB is needed initially. VirtualBox allows “dynamically allocated disks” which are faster to create and can grow to larger sizes. For example, if you set 50GB as your disk space (but only use 10 GB) then it will only occupy 10 GB on your Mac.