Update build instructions in the README

Author: Zephiles

README.md

@@ -15,10 +15,12 @@ See the [user manual](https://github.com/Zephiles/TTYD-Practice-Codes/blob/maste
 To build this, you need to have devkitPPC installed. Instructions for doing so can be found [here](https://devkitpro.org/wiki/Getting_Started). You also need to place **elf2rel.exe** in the **bin** folder. This file can either be compiled manually, or downloaded from [here](https://github.com/PistonMiner/ttyd-tools/releases/download/v2.5/elf2rel.exe).
 
 ## Building
-To build, navigate to the root directory of the repository (the folder with the makefile in it) and run `make`. Any combination of rules can be applied to this.
-`make us`
-`make jp eu`
-`make us eu`
+To build, you must first add **DEVKITPPC** and **TTYDTOOLS** to your environment. **DEVKITPPC** should be set to the `devkitPPC` folder, and **TTYDTOOLS** should be set to the `ttyd-tools` folder. Then, navigate to the root directory of the repository (the folder with the makefile in it) and run `make`. Any combination of rules can be applied to this. You should also run `make clean` after making any changes, as files built with a previous build could cause issues.  
+
+Examples of `make` being used:  
+`make us`  
+`make jp eu`  
+`make us eu`  
 
 ## Special Thanks
 * **PistonMiner** for helping me with many C++ questions, and overall providing a ton of in-depth technical assistance.