Gragon

Can you tell me where to put this code to make it work ?

Hello, I'm searching since hours and can't find an answear so I'm asking you.

I would like to install librairies or script to my personnal server but i don't understand how to do it.
They put files in github but no one say how to install it. I also can't find any tutorials on youtube.

Can you show me for example how to add this:

Thank you in advance.

EDIT: I would also be pleased if you just forward me to a good explaining tutorial.