in The Layout > Page Elements:
Click Add a Gadget and the select HTML/JAVASCRIPT gadget. Paste the following code in content section and give your title e.g "Search", "Search this blog"

<div id="topsearch" class="floatright pngfix">
			<form id="searchform1" action="/search" method="get">
			<div>
			<input id="tops" onfocus="if ( this.value == this.defaultValue ) this.value = '';" value="enter keywords and hit enter" name="q" title="enter keywords and hit enter" onblur="if ( this.value == '' ) this.value = this.defaultValue" type="text"/>
			<input id="topsearchsubmit" value="Search" type="submit"/>
			</div>
			</form>
		</div>