How to Use UEFITool?

Hi I am trying to turn off my CFG-Lock and got stuck at this point of the tutorial - when it says "open your firmware", what does that mean exactly?

https://preview.redd.it/14hi2ljwed451.png?width=1349&format=png&auto=webp&s=2dd7a89d362a6325746e4a25ee718cc7fa017aeb