I dont understand Skills and need help

I see a lot of YouTube videos about skills and how to find them on GitHub, but I just can’t quite grasp when and how to use them. For example, I have a project I’ve built using Google apps scripts. In my head, I’d like to have a skill that reviews apps scripts and ensure everything is working the most effective and efficient way. I found a skill on GitHub that says it reviews apps scripts. Do I just download the skil folder from Git and place it in the root folder of my project, then /skill name, then prompt what I want it to do? Do I have to do the /load skill to to get it recognized every time I want to use it? Sorry, I know this is elementary. There are so many skills out there that I am confused how to best apply them to my work. I have no doubt I’m wasting tokens by not using them, so any help would be appreciated. Thank you