How to set as screen lock? VIVO : To ensure the screen lock can be used properly, for some models, users should turn on “ Show on lock screen ” and allow “ Start in background ” in “Permissions” of “Apps” (Settings). If you can’t find these two permissions, please ignore it and click “Apply” in Wallpaper Master directly.” OPPO : For some models, users should turn on “ Display pop-up Window ” in “Permissions” of “Apps” (Settings). If you can’t find this permission, please ignore it and click “Apply” in Wallpaper Master directly. XIAOMI : For some models, users should turn on “ Show on lock screen ” and allow “ Start in background ” in “Permissions” of “Apps” (Settings). If you can’t find this permission, please ignore it and click “Apply” in Wallpaper Master directly. How to cancel the screen lock? You can turn off the screen lock in the Settings of Wallpaper Master.