If using Microsoft® Exchange / Corporate sync, some screen lock options (e.g., face unlock, pattern, PIN) may be unavailable.
These steps can also be utilized to change your current screen lock setting.
From a Home screen, tap Apps (located in the lower-right).
From the Apps tab, tap Settings.
From the Personal section, tap Lock screen.
Tap Screen lock.
If presented with This device does not have a Google® account associated with it. If you forget your PIN, it cannot be sent to you and a factory reset will have to be performed to recover the device., select Add Google account now to setup the account before proceeding. To proceed without setting up a Google account, tap Continue.
If presented, enter the current PIN/password/pattern.