To manually connect, do the following:

1. Create the Application Insights resource within the resource group and location nearest to your function app
2. Copy the Application Insights instrumentation key from the Application Insights resource
3. In the function app application settings, add a new app setting called APPINSIGHTS_INSTRUMENTATIONKEY and as value set to the Application Insights instrumentation key, and click on Save

When enabling Application Insights for your function app, it is advisable to disable built-in function logging, which uses Azure Storage. Built-in logging is useful when testing with a low workload in the development phase. To disable it, delete the AzureWebJobsDashboard app setting from the Azure Functions application configuration section.