As for outputting HTML in php:
<?php
echo "<p class='myTest' id='myTag'>This is some text within HTML-tags</p>";
// Notice the use of "" and '', you do not wanna close the echo adding a class or such
?>
and as for the CSS, start by including a stylesheet in your HTML-file (in the <head>
tag):
<link rel="stylesheet" type="text/css" href="myStyle.css">
and in myStyle.css, to style your HTML:
p.myTest {
color: red;
/* All <p> tags content with the class myTest will be written in red */
}
If you wish for your styling to be tag-specific:
p {
color: red;
/* All <p> tags content will be written in red */
}
Or maybe you'd like for it to be applied to a unique id instead:
#myTag {
color: red;
/* The content of the tag with the id "myTag" will be colored red,
given that color is a valid property for that specific tag */
}
There are loads of basic styling tutorials and guides out there to help getting you started styling that navbar.