add instruction

Signed-off-by: Nfangyun <fangyun2@huawei.com>

zh-cn/application-dev/reference/apis/js-apis-enterpriseDeviceManager-DeviceSettingsManager.md

@@ -6,6 +6,16 @@
 > 
 > 本模块首批接口从API version 9 开始支持。后续版本的新增接口，采用上角标单独标记接口的起始版本。
 
+## 使用说明
+
+通过enterpriseDeviceManager中getDeviceSettingsManager方法获取。
+
+```js
+import enterpriseDeviceManager from '@ohos.enterpriseDeviceManager'
+
+let deviceSettingsMgr = enterpriseDeviceManager.getDeviceSettingsManager();
+```
+
 ## DeviceSettingsManager.setDateTime
 
 setDateTime(admin: Want, time: number, callback: AsyncCallback<void>): void