how to add loading screen in html code example

Example: loading screen html

.loaded #loader-wrapper .loader-section.section-left {
    -webkit-transform: translateX(-100%);  /* Chrome, Opera 15+, Safari 3.1+ */
    -ms-transform: translateX(-100%);  /* IE 9 */
    transform: translateX(-100%);  /* Firefox 16+, IE 10+, Opera */
}
 
.loaded #loader-wrapper .loader-section.section-right {
    -webkit-transform: translateX(100%);  /* Chrome, Opera 15+, Safari 3.1+ */
    -ms-transform: translateX(100%);  /* IE 9 */
    transform: translateX(100%);  /* Firefox 16+, IE 10+, Opera */
}