How do I add filters to images?

$black-100: rgba(0,0,0,1);
$black-90: rgba(0,0,0,0.9);
$black-80: rgba(0,0,0,0.8);
$black-70: rgba(0,0,0,0.7);
$black-60: rgba(0,0,0,0.6);
$black-50: rgba(0,0,0,0.5);
$black-40: rgba(0,0,0,0.4);
$black-30: rgba(0,0,0,0.3);
$black-20: rgba(0,0,0,0.2);
$black-10: rgba(0,0,0,0.1);

$white-100: rgba(255,255,255,1);
$white-90: rgba(255,255,255,0.9);
$white-80: rgba(255,255,255,0.8);
$white-70: rgba(255,255,255,0.7);
$white-60: rgba(255,255,255,0.6);
$white-50: rgba(255,255,255,0.5);
$white-40: rgba(255,255,255,0.4);
$white-30: rgba(255,255,255,0.3);
$white-20: rgba(255,255,255,0.2);
$white-10: rgba(255,255,255,0.1);

//Invisible
$transparent: rgba(255,255,255,0);

//COLORS
$light-grey: #e0dfe1;
$light-grey-A: #f0f0f0;
$grey: #9f9e9f;
$dark-grey: #222222;
$white: #ffffff;
$blue: #0190ec;

//BMW
$light-blue: #6295ca;
$dark-blue: #13274c;
$red: #d1253b;

//ANIMATIONS stuff
$hover: all 0.2s ease-in;
$slide: all 0.3s cubic-bezier(.55,0,.1,1);
$slide-delay: all 0.4s 0.1s cubic-bezier(.55,0,.1,1);
$slide-slow: all 0.5s cubic-bezier(.55,0,.1,1);
$zoom: all 1s cubic-bezier(.55,0,.1,1);
$zoom-slow: all 2.4s cubic-bezier(.55,0,.1,1);
//MIXINS
// ADDS A BROWSER PREFIX TO THE PROPERTY
@mixin css3-prefix($property, $value) {
-webkit-#{$property}: #{$value};
-khtml-#{$property}: #{$value};
-moz-#{$property}: #{$value};
-ms-#{$property}: #{$value};
-o-#{$property}: #{$value};
#{$property}: #{$value};
}
// TRANSFORM
@mixin transform($params) {
@include css3-prefix(‘transform’, $params);
}
//FONT IMPORT
@import url(https://fonts.googleapis.com/css?family=Noto+Sans:400,700);

body {
background-color: lighten($dark-grey, 10%);
padding: 50px 0;
font-family: ‘Noto Sans’, sans-serif;
text-align: center;
}

//
.container {
background-color: $dark-grey;
margin: 0 auto;
width: 100%;
max-width: 320px;
min-height: 568px;
margin: 0 auto;
border-radius: 8px;
position: relative;
overflow: hidden;
-webkit-box-shadow: 0px 9px 13px 0px $black-30;
-moz-box-shadow: 0px 9px 13px 0px $black-30;
box-shadow: 0px 9px 13px 0px $black-30;
-webkit-transform: scale(1);
}

.menu-trigger, .close-trigger {
position: absolute;
top: 32px;
right: 20px;
display: block;
width: 42px;
height: 42px;
cursor: pointer;
z-index: 333;

&:hover {
.menu-trigger-bar {
&:before {
width: 100%;
}
}

.close-trigger-bar {
&:before {
width: 100%;
}
}
}
}

.close-trigger {
z-index: 5;
top: 42px;
}

.menu-trigger-bar {
display: block;
width: 100%;
height: 4px;
background-color: $white-100;
margin-bottom: 6px;
transform: rotate(-45deg);
position: relative;

&:before {
content: “”;
position: absolute;
top: 0;
left: 0;
display: block;
width: 0%;
height: 100%;
background-color: $black-20;
transition: $slide;
}

&.top {
width: 50%;
}
&.middle {
&:before {
left: auto;
right: 0;
}
}
&.bottom {
width: 50%;
margin-left: 50%;
}
}

.close-trigger-bar {
display: block;
width: 100%;
height: 4px;
background-color: $dark-grey;
position: relative;

&:before {
content: “”;
position: absolute;
top: 0;
left: 0;
display: block;
width: 0%;
height: 100%;
background-color: $white-20;
transition: $slide;
}

&.left {
transform: translateX(100px) translateY(-100px) rotate(-45deg);
}
&.right {
transform: translateX(-100px) translateY(-100px) rotate(45deg);
top: -3px;
}
}

.logo {
display: block;
width: 64px;
height: 64px;
position: absolute;
top: 50%;
left: 50%;
margin-top: -52px;
margin-left: -32px;
text-align: center;
z-index: 10;

span {
display: block;
text-align: center;
line-height: 62px;
font-size: 72px;
color: $white-100;
}
}

.logo-title {
position: absolute;
top: 10px;
left: 0;
width: 100%;
height: 100%;
color: $dark-grey;
font-size: 32px;
line-height: 82x;
}
.logo-badge {
position: absolute;
display: block;
width: 24px;
height: 24px;
top: 6px;
right: -6px;
border-radius: 100%;
background-color: $light-blue;
font-size: 12px;
line-height: 2;
text-align: center;
}

.inner-container, .menu-container {
position: absolute;
height: 100%;
width: 100%;
left: 0;
top: 0;
}

.inner-container {
z-index: 20;
}
.menu-container {
display: flex;
align-items: center;
}
.menu {
display: block;
width: 100%;
padding: 20%;
//opacity: 0;
//visibility: hidden;

li {
text-align: left;
display: block;
padding: 15px 0;
}

a {
text-decoration: none;
color: $dark-grey;
display: inline-block;
padding: 10px 0;
position: relative;

&:hover {
&:before {
opacity: 1;
transform: translateX(0px);
}
}

&:before {
content: “”;
display: block;
position: absolute;
left: 0;
bottom: 0;
width: 18px;
height: 4px;
opacity: 0;
background-color: $dark-grey;
transform: translateX(100px);
transition: $slide;
}
}
}

.menu-bg {
position: absolute;
display: block;
width: 200%;
left: -53%;
top: -25%;
//top: -25%;
height: 40%;
background-color: $white-100;

&.middle {
top: 29%;
left: -53%;
transform: rotate(-45deg) scaleY(0);
}
&.top {
left: -34%;
top: 0;
transform: rotate(-45deg) translateY(-152%);
//top: -25%;
}
&.bottom {
//bottom: 0;
top: 105%;
transform: rotate(-45deg) translateY(25%);
left: -20%;
}
}

#links{position:absolute;bottom:0px;left:0px;width:100%;height:50px;font-size:13px;font-family:tahoma;color:#fff;}
#links a{text-decoration:none;font-size:2.3em;color:#fff;}
#twitter{position:absolute;bottom:15px;right:20px;}
#pens{position:absolute;bottom:15px;left:20px;}

How do I use this code in fullscreen theme?I want to use the mobile menu icon in computer mode.