Onboarding Microsoft Sentinel starts by enabling Sentinel on an existing Log Analytics workspace and then connecting data sources so analytics can operate on ingested security data. Microsoft’s Sentinel onboarding guidance emphasizes that after you add Sentinel to a workspace, you must “connect Microsoft services, non-Microsoft solutions, and custom sources” using built-in data connectors. Microsoft also states that “you need data in your workspace before you can use Microsoft Sentinel’s analytics, hunting, and investigation capabilities.” Features such as custom analytics rules, hunting queries, and incident correlation depend on ingested telemetry from sources like Microsoft Entra ID sign-in logs, Microsoft 365, Defender products, firewalls, and other appliances. Because the question already gives you a Log Analytics workspace (the prerequisite for enabling Sentinel), the first action in the onboarding workflow that unlocks Sentinel’s value is to connect your security sources. Only after data is flowing should you proceed to create analytics rules, hunting queries, and incident processes. Therefore, the correct first step to onboard Microsoft Sentinel is connect to your security sources.