How to prevent indexing pages on WP platform?

I have a simple blog, with some posts and 3 pages (about, Contact, privacy).
How can i prevent indexing this 3 sites?

I have putted this code to pages template, first line:

PHP:

<meta name="robots" content="noindex">

Will this work?

 

a robot text file? there are some WP plugins for it

 

Yes, there are...but i don't want use plugins. (don't ask why )

 

Yes, it works

 

Thanks for confirmation.