Adding Google Tag Manager to Wordpress site?

Dear forum members,

I’m suuposed to add google tag manager code snippet in HTML files. Ok, anyone an idea in what Wordpress file to add it as they all dynamic php files?

Google says it has to be added in every page.

Copy the code below and paste it onto every page of your website. Place it immediately after the opening <body> tag.

Thank you for help on this!

It’s a long time since I messed with WP, but from memory, the <body> tag appears in the header.php file. The various parts of a WP page are stored in various files, so you have to look inside them and check where the bit you want to edit resides.