How do you make a lua file?

I download Citizen Models(the hexed one)and want to try use but it dint show the models?
I go to youtube and i watch this video
And i watch and i need a lua file but i dont know how to make one.
Can anyone help?

Yes. Notepad can help you here.
Open it.
Type what ever you need. Save as a .lua and ya done.

ok thanks