Added requirement to enable UEBA

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cc: @yelevin

Author: yelevin

articles/sentinel/anomalies-reference.md

@@ -25,6 +25,8 @@ Microsoft Sentinel uses two different models to create baselines and detect anom
 
 Sentinel UEBA detects anomalies based on dynamic baselines created for each entity across various data inputs. Each entity's baseline behavior is set according to its own historical activities, those of its peers, and those of the organization as a whole. Anomalies can be triggered by the correlation of different attributes such as action type, geo-location, device, resource, ISP, and more.
 
+You must [enable the UEBA feature](enable-entity-behavior-analytics.md) for UEBA anomalies to be detected.
+
 - [Anomalous Account Access Removal](#anomalous-account-access-removal)
 - [Anomalous Account Creation](#anomalous-account-creation)
 - [Anomalous Account Deletion](#anomalous-account-deletion)