Hi,
Under Monitoring -- Diagnostic settings, please click Add diagnostic setting, select categories you want, select Send to Log Analytics workspace for destination, and choose your workspace.
If necessary you can exit out and create a new Log Analytics workspace. After creating the workspace you can start the above steps over and choose your newly-created workspace. You will need to refresh the page after creating a workspace because the diagnostic settings blade will only show the workspaces that existed when you opened it.
Please see article below for more detailed information:
Send logs to Azure Monitor
Please note there is a delay before data will flow to the workspace and thus show up in query results. Sometimes log data will start to show up within a few minutes, other times it can take substantially longer. The docs say it can take up to 90 minutes for it to start working.
Please click Accept Answer if the above was helpful.
Thanks.
-TP