I was having trouble finding the unlock security settings but I finally had success!
1) Installed and launched MySettings from Side Me
2) The first time I clicked the MySettings lock icon, I got the normal "Location and security settings" screen.
3) I previously had set the credential store password. This time I also enabled "Use secure credentials".
4) Now when I click the MySettings lock icon, I get the "Screen unlock security" settings screen.