The following code works a dream loading it in the (Style Manager) -> Navbar which adds the search towards the right (opposite the logo) in my header.
Code:
<!-- New Header Search Input -->
<form action="search.php" method="post">
<input type="hidden" name="do" value="process" />
<input type="hidden" name="showposts" value="0" />
<input type="hidden" name="quicksearch" value="1" />
<input type="hidden" name="s" value="" />
<input type="hidden" name="securitytoken" value="$bbuserinfo[securitytoken]" />
<input type="text" class="bginput" name="query" size="20" value="$search[query]"/> <input type="submit" value="Search Forum" />
</form><br><span align="right" class="smallfont"><a href="search.php?">Advanced Search</a> </span>
<!-- New Header Search Input -->