Please always provide a link to your site so we can see what other elements are present.
One way is to use Main Options > HEader > Header HTML , then move it over the header image following item #2 in the tutorial below
To make it a link you need to use the proper HTML for that. If you do not know any HTML search HTML reference sites. The basic HTML syntax for a link is
<a href=”LinkUrl“>The text</a>