Legacy doesn't have the code for mobile menu icon?

Hello,
I don’t see the Responsive Menu code in Legacy’s style.css (like I do in your Epik Theme).

If I wanted to add that option, would it just be a matter of adding this code to the css? Are there any changes that need to be made to any other files?

Thank you!

/* Responsive Menu
--------------------------------------------- */

.responsive-menu-icon {
	cursor: pointer;
	display: none;
	margin-bottom: 10px;
}

.responsive-menu-icon::before {
	color: #fff;
	content: "\f333";
	font: normal 32px/1 'dashicons';
	margin: 0 auto;
}

and

	.genesis-nav-menu.responsive-menu {
		display: none;
	}

	.nav-primary .responsive-menu-icon {
		margin-top: 20px;
	}

	.genesis-nav-menu.responsive-menu .menu-item,
	.responsive-menu-icon {
		display: block;
	}

	.genesis-nav-menu.responsive-menu .menu-item:hover {
		position: static;
	}

	.genesis-nav-menu.responsive-menu li.current-menu-item > a,
	.genesis-nav-menu.responsive-menu .sub-menu li.current-menu-item > a:hover,
	.genesis-nav-menu.responsive-menu li a,
	.genesis-nav-menu.responsive-menu li a:hover {
		border: none;
		display: block;
		padding: 20px;
		text-transform: none;
	}