My Path: C:\Users.......\Desktop......\coding\font-awesome-4.7.0\css

my header code:

<div id="slideout-menu">
    <ul>
        <li>
            <a href="<?php echo site_url(''); ?>">Home</a>
        </li>
        <li>
            <a href="<?php echo site_url('/blog'); ?>">Blog</a>
        </li>
        <li>
            <a href="<?php echo site_url('/projects'); ?>">Projects</a>
        </li>
        <li>
            <a href="<?php echo site_url('/about'); ?>">About</a>
        </li>
        <li>
              <input type="text" placeholder="Search Here">
        </li>
    </ul>
</div>

<nav>
    <div id="logo-img">
        <a href="#">
            <img src="<?php echo get_template_directory_uri(); ?>/img/logo.png" alt="GTCoding Logo"> 
        </a>
    </div>
    <div id="menu-icon">
        <i class="fa fa-bars"></i>
    </div>
        <ul>
            <li>
                <a href="<?php echo site_url(''); ?>"
                    <?php if(is_front_page()) echo 'class="active"' ?>
                >Home</a>
            
            </li>
            <li>
                <a href="<?php echo site_url('/blog'); ?>"
                <?php if(get_post_type() == 'post') echo 'class="active"' ?>
                >Blog</a>
            </li>
            <li>
                <a href="<?php echo site_url('/projects'); ?>"
                <?php if(get_post_type() == 'project') echo 'class="active"' ?>>Projects</a>
            </li>
            <li>
                <a href="<?php echo site_url('/about'); ?>"
                <?php if(is_page('about') == 'post') echo 'class="active"' ?>
                >About</a>
            </li>
            <li>
                <div id="search-icon">
                    <i class="fa fa-search"></i>
           
                </div>
            </li>
        </ul>
    </div>
</nav> 

<div id="searchbox">
    <input type="text" placeholder="Search Here">
</div> 

<?php if(is_front_page()); { ?>
   <main> 
<?php } ?>