Go into the phones settings menu and look for the lockscreen & security setting and click on it.
Then right at the top you should see lock screen type, click on that and there you will be able to change your lock type for your lockscreen.
Hi Donna, go to apps>settings>lock screen> screen lock>enter your pin>continue> touch none. This should undo the lock screen. Hope that helps! Also I thought I'd mention that the s5 has a fingerprint scanner. :)