How can I add a logo to this site that is stretches from one side of the header to the other

This site will not allow me to upload a header image (set at 0px height) and the logo is apart of a 1/3 column and I can’t figure out how to get it to reach end to end without jacking up the header. Here is what I’m going for compared to what’s currently on the site.

I was getting help with this question with you and I was asked to allow for support access. Are you able to access the dashboard?