Update README.md with compilation instructions

README.md

@@ -1,2 +1,17 @@
 # nsmb2-patch-collection
-A collection of publicly available code patches for New Super Mario Bros. 2.
+A collection of publicly available code patches for New Super Mario Bros. 2, for use in custom levels.
+
+These patches were not created by me, except for the up/down skewer patch. Credits go to @RicBent for the rest of them.
+
+All patches are created for the US Gold (0004000000137E00) version of the game, but IPS patches for all regions are provided on the Releases page.
+
+# Compiling
+
+NOTE: Compiling at the moment only works on Linux (and maybe macOS).
+
+1) Compile (or download) [Magikoopa](https://github.com/RicBent/Magikoopa).
+2) Clone this repository.
+3) Download a standalone version of the [GNU Arm Embedded Toolchain](https://developer.arm.com/downloads/-/gnu-rm), and unzip it inside this repository. You should have a `gcc-arm-none-eabi` folder next to the `source`, `loader`, etc. folders.
+4) Copy your game's `code.bin` and `exheader.bin` into this directory as well.
+5) Open Magikoopa, and set the working directory to the respository folder (containing your `code.bin`).
+6) Press "Make and Insert". Your code files will now be patched, and a backup of the originals will be kept in `bak`.