you install and open Go Launcher and then the next time you hit the home key (or virtual key) it will ask you which launcher you want to use, either stock or Go, just select 'use default' checkbox and click Go. it's a really nice launcher with tons of great free themes, and is constantly updated. they also recently added a security detection front-end to verify software is secure and safe
the first time I used Go Locker all I had to do was run it in the app list then it usually goes through a preview slideshow of what it does then shows the default locker theme and you slide to unlock--it's usually on by default once you launch it from within go launcher.
Samsung Galaxy Precedent (rooted, AreaRom 3.4 , sd-ext w/ 3.65GB internal space)
Kindle Fire (1st Gen, rooted, AOKP JB 4.1, Nova Launcher)
Samsung Galaxy SIII 4G LTE (rooted, Carbon ROM)