Easy way is to use the web.conf file in the Azure application services wwwroot directory as a place.
Just put the following texts on the wwwroot/web.conf file and restart the service.
<?xml version="1.0" encoding="UTF-8"?>
<configuration>
<system.webServer>
<rewrite>
<rules>
<!-- BEGIN rule TAG FOR HTTPS REDIRECT -->
<rule name="Force HTTPS" enabled="true">
<match url="(.*)" ignoreCase="false" />
<conditions>
<add input="{HTTPS}" pattern="off" />
</conditions>
<action type="Redirect" url="https://{HTTP_HOST}/{R:1}" appendQueryString="true" redirectType="Permanent" />
</rule>
<!-- END rule TAG FOR HTTPS REDIRECT -->
</rules>
</rewrite>
</system.webServer>
</configuration>