Place Login button

Hey everybody!
I’ve recently installed the Place Login plugin which shows up as a login form at the sidebar of my blog. However, the plugin’s creator says that I an add a button login in any part of my web page by adding this code in my template files:
<?php if ( function_exists( ‘plogin_form’ ) ) plogin_form(); ?>.

I’m new to all of this so I don’t really know how/where to add this piece of code, or what a template file is exactly. I’ve purchased the Avada theme, and any help to lead me in the right direction would be greatly appreciated.