You can install devkitPro's toolchains using the installers linked from their getting started page. You can download the latest Visual Studio from https://visualstudio.microsoft.com or the link in that guide still seems to work for 2008, the wizard to add DS projects isn't even on archive.org though...
Their recommended setup is rather out of date though saying as the tutorial is from 2012, what I personally use for DS homebrew is:
- devkitPro's nds-dev toolchain which can be installed using pacman, install pacman using the method for your OS from their getting started page
- Visual Studio Code
-- You can use any text editor or full Visual Studio if you want, this is my personal favorite for DS projects though as its cross platform and works quite well, probably a nicer experience than Visual Studio 2008, just run 'make' from the terminal to build things instead of pressing F7
- If you want you should be able to use NightFox Lib too, I think it still works, I haven't used it myself though