Need some Help: How do I download windows 10 on an external drive for the 2018 Macbook Pro?

For Reference, I am using the 2018 Macbook Pro. Recently, I wanted to keep the windows and Mac parts of my computer separate, and I heard that you could do so by getting an external drive. I have purchased a SanDisk 2TB drive for my windows partition, however, every single tutorial on how to do this is either wrong, or works with the caveat of major features being missing. I was wondering if anyone in this subreddit would know of a tutorial or have some way to help me.