
Explanation

Box 1: From the Scale up (App Service Plan) settings blade, change the pricing tier The B1 pricing tier only allows for 1 core. We must choose another pricing tier.
Box 2: From the Scale out (App Service Plan) settings blade, enable autoscale
1.
Log in to the Azure portal at http://portal.azure.com
1. Navigate to the App Service you would like to autoscale.
2. Select Scale out (App Service plan) from the menu
3. Click on Enable autoscale. This activates the editor for scaling rules.

Box 3: From the Scale mode to Scale based on metric, add a rule, and set the instance limits.
Click on Add a rule. This shows a form where you can create a rule and specify details of the scaling.
References:
https://azure.microsoft.com/en-us/pricing/details/app-service/windows/
https://blogs.msdn.microsoft.com/hsirtl/2017/07/03/autoscaling-azure-web-apps/