How to Access Dolphin Source Code?

[Slippy]

Hi, I had a question wondering how I can access the Dolphin Source code and modify the ActionReplay.cpp file. There is a mod to Metroid Prime 1 and 2 I would like to add, and it requires access to said .cpp file. I can find it easily on GitHub, but have no idea how to access it from my end. Thanks.

For info on the mod installation, if it will help, here it is: https://www.reddit.com/r/DolphinEmulator/comments/7fbcsl/classic_fpsstyle_metroid_prime_trilogy_code/