How to add a pic to the header in Mystique?

Unless you provide a link to a page demonstrating the problem, no one will be able to offer much in the way of specific help.

You could try uploading a small image called something like header.jpg to your theme’s images folder. Then editing the theme’s stylesheet and changing:

#header {
display:block;
height:180px;
position:relative;
z-index:5;
}

to

#header {
display:block;
height:180px;
position:relative;
z-index:5;
background:url(images/header.jpg) no-repeat right top;
}

The image needs to be small (approx 100px square) as you don’t have much room left in that header.

If you are using mystique you can either modify this file: http://www.yousite.com/wp-content/themes/mystique/images/header.jpg or upload your own 1300×400 pixel graphic to look however you want it to look, ie with a photo next to your logo. Not so hard!