Template dropdown option missing from page attributes

Hello,

I am completely new to WP and currently following a guide to set up my first site from scratch locally on my desktop. I have arrived at the stage where i am looking to update the page layout (for my homepage to front page layout) but am unable to do so as the ‘template’ drop down is missing from the page attributes section on the page editor.

I am currently working with the ‘twenty sixteen’ default theme.

I have tried a number of updates to in the editor section (functions.php and page.php) adding the following code as advised on previous forums;

<?php
/*
Template Name: My Custom Page
*/
?>

This added the drop down but doesn’t seem to change any setting when selected, and as a complete beginner i’m unsure as to what to do next

Would it be possible for someone to outline a ‘dummies’ guide to rectify this situation please?

Any help would be very welcome and prevent me from going insane!

Thanks
Pete