I'm trying to call the main website template (portal.frontend_layout) and to change the header using an xpath tag to replace the content for my custom content but I can't do it.

<div id="wrapwrap" class="homepage ">
<header class=" o_affix_enabled">
<nav class="navbar navbar-expand-md navbar-light bg-light">
<div class="container">
......

Any one has any example for building the main template of a website from scratch?

Thanks!