Step 1: Add the following to your Header.php file after navigation paragraph.

<div class=“header-search“><?php get_search_form(); ?></div>

Step 2: Add the following to your Style.css file.

/* This is gonna define the CSS of search box */
@media screen and (min-width: 600px) {
.header-search {display:block; float:right; margin-top:-12px; margin-right:3px;}}

/* This is definition of search button */
#searchsubmit {
background-color: #fff;
color: #000;
border: 1px solid #ff7700

Step 3: Put the search box to a suitable place by modify the CSS code above.