is there a code? like you click on them and write something?? what is it? thanks

You don't.

The closest you get is companion mods for PC, but they hardly cover all NPCs.

Are you talking about a mod? Or are you playing normally?

hmm... Im on pc.. is there any mods that you know of? I typed setplayerteammate 1 and it appeared with the companion dialog but then they will just not follow me

I am playing normally but I can install a mod to do it.. is there any mods that you know of that let me do this?

Being a companion is much more than just one variable. It includes scripts, AI Packages, more scripting, dialogue and all that.
I haven't played NV nearly as much as FO3, but I know one companion mod for NV that lets you recruit one of the vanilla characters - Sunny Smiles:
http://newvegasnexus.com/downloads/file.php?id=37281

thank you.. sunny is who I wanted to recruit in the first place! thanks alot
:D

There is a mod that actually lets you literally click on anyone and make them your companion, even kids and animals, but it's part of a bigger mod who's name escapes me now, I think i8t's the real time settler mod, I'm not exactly sure

Fallout 3 had a more practical mod which allowed you to recruit anyone who you could engage in menu dialogue with.

I like to call it "At gunpoint"

yep they have a bunch of companion mods for pc