how do i install custom player models?? and just mods in general

there's no tutorials for team fortress 2 classified, only for tf2. i tried adding a "custom" folder like tf2 tutorials said to do, but this popped up. there is no "readme.txt", the only thing in the custom folder is the files i added.

https://preview.redd.it/tisbnwqirkjg1.png?width=621&format=png&auto=webp&s=420fae1fb2ce872a8e3d2b1ff3ea360aeb4a4710