How can I apply CSS style using ID value?

you can use id in your html element in which you want to give style:
<input id="button" type="submit" value="Go" name="goButton">
then in your style sheet, you should use:
#button {
Color: white;
background: red;
font-size: 15px;
border-radius: 4px;
padding: 5px 10px;}

CSS
#identified {
background-color: skyblue;
}

HTML
<div id="identified">This div has a special ID on it!</div>
<div>This is just a regular div.</div>