In your header.php search for this line:
That is the function call to output the theme logo you set in the backend or the default one. Looking at your example, I would suggest just commenting that out or deleting it. Then go up a few lines to where you see:
You can add your new logo content in between those two so that you don't have to bother with php and can just add in the straight html/css. So something like:
<h1 class='logo'><a href='http://envisage-design.co.nz/'><img src=http://18.104.22.168/envisage-design.co.nz/images/logo3.jpg alt='' /></a></h1>
Then you can change the logo H1 to your other logo area design and modify the CSS to adjust it as needed. Keep your css changes to custom.css in the css folder and save a copy of the header.php so that when you update the theme in the future you can re-add these changes.