[Jack12]

All depends on exactly what you're trying to change.

Checked my uploaded image. Red square is an image and can only be edited through a image manipulation program.

Green square is controlled by the Site Name option.

If you want to just change the title in the green square, you can do so by editing the forumhome template.

<div id="pagetitle">
		<h1>{vb:raw vboptions.bbtitle}</h1>
		<p id="welcomemessage" class="description">{vb:rawphrase welcome_to_the_x, {vb:raw vboptions.bbtitle}}</p>
	</div>

Change {vb:raw vboptions.bbtitle} to the text you want to appear.