Moved WordPress Website to another Hosting

I did a full backup of my WordPress website from one hosting company and had another hosting company restore that to their system.

I need to change the Aweber code for the Optin on the page that is displayed when you type in my URL, https://www.dogfoodrecipessite.com

I find no way to see that source code so I can put the new Aweber webform code into that page.

How can I see that pages source code and make changes to it?