And how do you change the font without completely messing up the neatness of the site? for example; I want to change the Header titles like "Your Mailbox" to Book Antiqua, but after my research I couldnt find a font-family code for that font ):
Please help, thank you so much <3

For your first question: when starting from the 'Default' palette, add the following line between the curly braces { } following the body selector (change the highlighted part to whatever 6-character hex code you want!):

background: #455b2e;

Make sure to delete the following line:

background-image:url("../images/hee_bg.jpg");

For example, your end result might look like:

body {

background: #455b2e;

}

For a nice reference on how to style backgrounds, see https://developer.mozilla.org/en-US/docs/Web/CSS/background

Regarding your second question, try adding the following line within the curly braces of .headline (under the category 'Page Name text')

font-family: palatino, serif;