Hi There,
Please add the zezame-left
class to your column contains the mailchimp form:

After that add this custom CSS under Theme Options > CSS:
.zezame-left form {
background: white;
width: 100%;
padding: 5px 10px;
border-radius: 8px;
box-shadow: 6px 7px 10px black;
margin-top: 22px;
}
.zezame-left .mc4wp-form-fields p {
margin: 0;
}
.zezame-left .mc4wp-form-fields p:nth-child(1) {
width: 63%;
float: left;
}
.zezame-left form input[type="email"] {
border: none;
font-family: open-sans;
color: black;
box-shadow: none;
margin: 0;
outline: none;
}
.zezame-left form input[type="submit"] {
background-image: url(https://zezame.io/wp-content/uploads/2018/07/button.png);
border: none;
color: white;
font-family: open-sans-medium;
width: 35%;
padding: 7px;
background-size: 100% 100%;
border-radius: 9px;
}