(SOLVED)Help with Missing Assembly References

[Kuratheris]

So I've got zero experience with making a .DLL assembly mod, but I'm trying to edit the Cupro's Stones 1.0 source found here: https://github.com/Benjamin-S/Cupros-Stones/releases to give mod options to my stones mod.

I can open it and edit it with Visual Studio 2017, but I'm having some issues.
1: I've copied Assembly-CSharp.dll and UnityEngine.dll from the Rimworld Managed folder, and put them into the Cupro's Stones source at Cupros-Stones-1.0\Source\CuprosStones\Source-DLLs, but it still says they aren't found in Visual Studio when I open the sln file.

2: I have no idea how to compile it into a DLL when/if I do manage to tweak it.

Also if it's more complicated than just editing everything I need to, compiling it, and adding code to my mod for it, please do tell.

[Mehni]

https://rimworldwiki.com/wiki/Modding_Tutorials/Setting_up_a_solution