How to install Haxchi (Or CBHC)

Why? I thought it would be fun to make a guide like this! :D

IMPORANT: With the closure of the eShop for Wii U and 3DS, It is no longer possible to purchase any new DS VC game. Therefore the only way to install Haxchi is if you already have had a compatible DS game from before.

What's required:

A legally purchased DS Virtual Console game compatible with Haxchi (most common is Brain Age)
An SD Card (Recomended 32 GB)
A device such as a computer that can transfer files to the SD card.
A Wii U with internet access

SD Prep:

This section will place