I will assume you are already have deployed the applications at Azure Web App, but it show nothing at Log Stream. Here is the Log stream looks.
Log stream menu under Monitoring section.
When you have warning about the App Service logs not activated, you come to the right place. You need to go App Service logs menu under Monitoring section .
Click the Application Logging menu to File System. Define the Quota (MB) and Retention Period (Days) with your needs, as my example fill about 35 MB and 5 Days, I fill low number because this is only for testing/development for the Production maybe you will need higher quota and longer retention period. After finished, you can try again into Log stream and also do any tasks that will trigger the logs.
Anyway, this step only to find the logs same as Log stream , but not about to activate it.
Visit this: https://.scm.azurewebsites.net/
You will get pages like this
You can try check the logs by click Current Docker logs or if you need download the logs, click Download as zip.
If you need more information about to get logs, it will good if you try to check the Azure Documentation. Here the link: https://docs.microsoft.com/en-us/azure/app-service/troubleshoot-diagnostic-logs
This is part of learning this module: https://docs.microsoft.com/en-us/learn/paths/az-400-develop-instrumentation-strategy/