To unlock the display, touch the padlock and type the key code you have set in the system profile.
The result of unlocking is an open padlock:
You may now tap it again to exit. If you delay, the display will lock again automatically after a few seconds.
Using Samsung Smart Signage Platform (SSSP)
When you use SSSP you can only use numeric keys. In this case the unlock popup will look like this:
Alternative to touching the padlock
On some displays, due to the location of the padlock, you may find it cumbersome to invoke the unlocking feature. In these cases, you may touch the time on the display instead. The same steps apply: