Remove FORUM: & Sub-Forum:

[findingpeace]

First step would be to open up the template where this occurs:

Forum Display Templates -> FORUMDISPLAY

Looks like this is the part you want:

<div id="pagetitle" class="pagetitle">
	<h1>{vb:rawphrase forum}: <span class="forumtitle">{vb:raw foruminfo.title}</span></h1>
	<vb:if condition="$foruminfo['description']"><p class="description">{vb:raw foruminfo.description}</p></vb:if>
</div>

Delete the bolded part (or comment it out).

As for renaming "Forum", you'd need to find the phrase "Forum" under languages / phrases, and edit that. Keep in mind, that word is going to be used in many other places in vB