Manage pages missing

I am trying to hide the sidebar from all pages except the homepage.

I have created another page.php and renamed it.

However, there is no option anywhere to select this page as an active page. I know there should be a page ‘manage’ section in the page editor where you can do this but it is missing!!!

It was there????? but now is not. I believe it may have been called ‘template’… p

Any help please before the rope in the corner starts to become attractive!

Thanks

ps.. not used wp before