As said above, no tools needed. Lightly push downward on the entire fitting to take a little pressure off and then squeeze in on the two white tabs at the very bottom of the fitting (like busterofknuckels said, you can just BARELY see one of them at the bottom in your picture)
Easy peasy. Sometimes they can get junk in there and make it impossible to press in the tabs.....in that case a 90* O Ring pick to pick the junk out and/or some compressed air will usually clean them out.
If you are having a hard time picturing what we are saying just look at your new line and it will become apparent what you need to do.