It looks like this project is built with DevkitARM and CTRULIB. You will need to install the DevkitARM toolchain from devkitpro (instructions here). The latest versions of DevkitARM actually come with ctrulib, but if you need a newer version, you can grab the source here, and build it with devkitarm, just read the instructions.
More generally, different projects are compiled with different toolchains and libraries, so you will need to learn how to read various types of build files (such as Make, CMake, or SCons to name a few common ones), to determine what tool chains they use. You will also need to familiarize yourself with some common toolchains, languages, and libraries in order to actually get everything you need. Also, having a general understanding of common command line tools is very useful. Most projects will have a nice set of build instructions that you can mostly just run one at a time, but with some projects, you just have to look at the code and figure out how to build it, and the only way to learn how to do this is experience.