Menu Item on Simple Blog

My question is related to the “Simple Blog” demo that is included with the Highend Theme. On the Simple Blog demo main menu, there is a icon at the far right. It looks like 3 stacked horizontal bars (see attached). When you click on it, it opens up a new window that allows you to search by text, tags, categories, etc.

My question: How do I implement one of these menu items.

Thanks in advance,
Todd