Once the SSL certificate is installed, your site still remains accessible via a regular insecure HTTP connection. To connect secure url you need to manually enter https:// prefix. To force a secure connection on your website you need to set redirect rule which redirects http to https.
You could follow below steps to redirect site from http to https:
Download Url rewrite module manually or from web platform installer.https://www.iis.net/downloads/microsoft/url-rewrite

Open IIS manager window and select site from connection pane which you want to apply redirect rule.
- Select URL Rewrite from feature view.

- Click Add Rule from Action pane in a rewrite module.
- Select Blank Rule in the Inbound section, then press OK.

- Enter the rule name.
In the “Match URL” section:
Select “Matches the Pattern” in the “Requested URL” drop-down menu
- Select “Regular Expressions” in the “Using” drop-down menu
- Enter the following pattern in the “Match URL” section: “(.*)”
- Check the “Ignore case” box
- In the “Conditions” section, select “Match all” under the “Logical Grouping” drop-down menu and press “Add” In the prompted window:
- Enter “{HTTPS}” as a condition input
- Select “Matches the Pattern” from the drop-down menu
- Enter “off” as a pattern
- Press “OK”
- In the “Action” section, select “Redirect” as the action type and specify the following for “Redirect URL”: https://{HTTP_HOST}{REQUEST_URI}
- Check the “Append query string” box.
- Select the Redirection Type.
- Click on “Apply” on the right side of the “Actions” menu.

You could also add this rule directly in web.config file withoud using UI module which mention above.
<configuration>
<system.webServer>
<rewrite>
<rules>
<rule name="HTTP to HTTPS" enabled="true" stopProcessing="true">
<match url="(.*)" />
<conditions>
<add input="{HTTPS}" pattern="off" />
</conditions>
<action type="Redirect" url="https://{HTTP_HOST}{REQUEST_URI}" redirectType="Permanent" />
</rule>
</rules>
</rewrite>
</system.webServer>
</configuration>
Regards,
Jalpa.