Twenty Fourteen – Edit Previous/Next Buttons

Hello

I have found on some forums that I can edit the previous/next post fields in the “inc/template_tags.php”
I have been successfully editing the theme through the child theme and I set up the file above too and did this adjustment:

previous_post_link( '%link', __( '<span class="meta-nav">PREVIOUS ACTION</span>%title', 'twentyfourteen' ) );
				next_post_link( '%link', __( '<span class="meta-nav">NEXT ACTION</span>%title', 'twentyfourteen' ) );

But it is not changing it, it still says Previous Post and Next Post.
Is there another edit/step that I need to do somewhere else?

Also, i would like to edit these two “buttons” to be side-by-side rather than above one another, would I be doing these edits in the css?

I hope I can get this to work.
Thanks