https://www.att.com/device-support/article/wireless/KM1296344/Samsung/GalaxyTab4T537A/
Samsung Galaxy Tab 4 (T537A) - Learn and customize the home screen - AT&T
Get Samsung Galaxy Tab 4 (T537A) support for the topic: Learn and customize the home screen. Find more step-by-step device tutorials on att.com.
samsung galaxy tab
https://zh.ifixit.com/Answers/View/672382/Reset+pin+for+administrator
Reset pin for administrator - Samsung-SM-T537A - iFixit
Forgot pin for administrator need to reset to access tablet - Samsung-SM-T537A
reset pinadministratorsamsungsmifixit