You are going to get alot of snarky comments as a little google searching can quickly get you a walk through on creating a dual boot system... but here are some thoughts that might be helpful:
Maybe it is time to rethink this direction you are going. A solution could be to use the Linux subsystem. This has many benefits including a much lower chance of you making the computer unbootable.
Getting the Kali on Win10 is easy enough: https://blogs.technet.microsoft.com/motiba/2018/03/07/setting-up-kali-linux-on-windows-subsystem-for-linux/
The only downside (and this is not trivial) is that many of the tools that Kali comes with need to be manually downloaded rather than just available to you built in... But I would think this is less likely to end in tears.
I think that MichaelBay is right, you might want to seriously read:
Why is Kali Linux so hard to set up? Why won't people help me?
If you wish to persist, this is totally doable. Be prepared to do this a few times to get it right, and have all your files backed up first. More importantly: You need to slow down, and follow a walk through to the 't'.
find some simple walk throughs
I suggest you watch a bunch of these until you can predict what they are going to say. You will learn about the many variations in how this is done. Then choose one, and follow it completely. You are not ready to free-style, and that is OK. Keep going, but also read (or watch) walk throughs. You will get stuck less, less frustrated, and get more done.