Two ways

You can install the current release Firefox 25.0.1 from mozilla.org

or 
You can change the channel it is on in a channel-prefs.js file while Firefox is closed.

http://forums.mozillazine.org/viewtopic.php?f=23&t=2280605

doesn't work. I tried the editing of channel-prefs.js while FF is closed, then re-booted my computer ... still shows ESR. Then did the HELP/ABOUT where is shows a link to change it ... the menu comes up, I select RELEASE, then close/open FF and still hasn't changed.

Hello, you can try also full installer from the next link, http://www.mozilla.org/en-US/firefox/all/

thank you

Help > About should show on which update channel you are if it is not the release update channel.

It is best to install the full version to switch the update channel and do a clean install by removing the Firefox program folder to remove all files.