We will now going to understand how to Add Page Templates in the Theme using an example of adding About Page Template. so let’s understand it in the following tutorial :

In WordPress Dashboard go to Pages submenu and click on Add New Page.

After clicking on it Add New Page will appear.

Now after reaching to this page , here you can Add a New Page and select Page Template as any Page you wish

Then click on Publish.

Please follow this Screenshot for Reference :