you have to turn it off in settings. you will stay on insider build until the public builds catch up. it won't change your current install from what it is now.
last time i did it, i downloaded the new public release iso and then installed that over the insider build. it will install just like any other "update" and you can select it to save files and settings if you wish.
that or a total fresh install from your usb drive if you wish to go that way.