Html 将子菜单添加到以前制作的css菜单

我有一个关于我的网站子菜单的问题。 CSS和HTML在任何地方都没有，我正在尝试添加它，但不确定确切位置。我的另一个担忧是，它在风格上与已经写的东西有很大的不同，我不确定它是否会把一切都搞砸

有人知道如何解决这个问题吗？ 非常感谢 格洛

菜单的css：

       .nav {
  font-size: 12px;
  letter-spacing: 0;
    text-transform: uppercase;
}

.nav ul {
  margin: 0;
  padding: 0;
  list-style: none;
}

.navigation:before, .navigation:after {
  content: " ";
  /* 1 */
  display: table;
  /* 2 */
}
.navigation:after {
  clear: both;
}
.navigation li {
  position: relative;
  z-index: 1000;
}
.navigation > li {
  float: left;
}
.navigation ul {
  position: absolute;
  z-index: 300;
  top: -999em;
}
.navigation li:hover > ul,
.navigation .sfHover > ul {
  top: 34px;
}
.navigation li li:hover > ul,
.navigation li .sfHover > ul {
  top: -2px;
  left: 100%;
}
.navigation li li li:hover > ul,
.navigation li li .sfHover > ul {
  top: 0;
  left: 100%;
}
.navigation a, .navigation .navigation a:visited {
  display: block;
  white-space: nowrap;
}
.navigation a {
  /* Global Menu Link Styles */
}
.navigation a:hover,
.navigation .sfHover > a {
  text-decoration: none;
  /* First Level & Global Menu Link Hover Styles */
}
.navigation > li > a {
  /* First Level Menu Link Styles */
  margin-right: 30px;
}
.navigation > li:nth-last-child(1) > a {
    margin-right: 0;
  }
.navigation > li ul a {
  background: #fff;
  padding: 8px;
  margin-bottom: 1px;
  letter-spacing: 1px;
  font-size: 10px;
  /* All Other Menu Level Link Styles */
}
.navigation > li ul a:hover,
.navigation > li ul .sfHover > a {
  background: #ebebeb;
  color: #161616;
  /* All Other Level Menu Link Hover Styles */
}
.navigation > li > a:hover,
.navigation > li.current-menu-item > a,
.navigation > li.sfHover > a,
.navigation > li.sfHover > a:active {
  color: #F80683;

     * Image sizes.
 */
add_image_size( 'olsen_light_square', 200, 200, true );

/*
 * Navigation menus.
 */
register_nav_menus( array(
    'main_menu'   => esc_html__( 'Main Menu', 'olsen-light' ),
    'footer_menu' => esc_html__( 'Footer Menu', 'olsen-light' ),
) );

/*
 * Default hooks

菜单的HTML：

       .nav {
  font-size: 12px;
  letter-spacing: 0;
    text-transform: uppercase;
}

.nav ul {
  margin: 0;
  padding: 0;
  list-style: none;
}

.navigation:before, .navigation:after {
  content: " ";
  /* 1 */
  display: table;
  /* 2 */
}
.navigation:after {
  clear: both;
}
.navigation li {
  position: relative;
  z-index: 1000;
}
.navigation > li {
  float: left;
}
.navigation ul {
  position: absolute;
  z-index: 300;
  top: -999em;
}
.navigation li:hover > ul,
.navigation .sfHover > ul {
  top: 34px;
}
.navigation li li:hover > ul,
.navigation li .sfHover > ul {
  top: -2px;
  left: 100%;
}
.navigation li li li:hover > ul,
.navigation li li .sfHover > ul {
  top: 0;
  left: 100%;
}
.navigation a, .navigation .navigation a:visited {
  display: block;
  white-space: nowrap;
}
.navigation a {
  /* Global Menu Link Styles */
}
.navigation a:hover,
.navigation .sfHover > a {
  text-decoration: none;
  /* First Level & Global Menu Link Hover Styles */
}
.navigation > li > a {
  /* First Level Menu Link Styles */
  margin-right: 30px;
}
.navigation > li:nth-last-child(1) > a {
    margin-right: 0;
  }
.navigation > li ul a {
  background: #fff;
  padding: 8px;
  margin-bottom: 1px;
  letter-spacing: 1px;
  font-size: 10px;
  /* All Other Menu Level Link Styles */
}
.navigation > li ul a:hover,
.navigation > li ul .sfHover > a {
  background: #ebebeb;
  color: #161616;
  /* All Other Level Menu Link Hover Styles */
}
.navigation > li > a:hover,
.navigation > li.current-menu-item > a,
.navigation > li.sfHover > a,
.navigation > li.sfHover > a:active {
  color: #F80683;

     * Image sizes.
 */
add_image_size( 'olsen_light_square', 200, 200, true );

/*
 * Navigation menus.
 */
register_nav_menus( array(
    'main_menu'   => esc_html__( 'Main Menu', 'olsen-light' ),
    'footer_menu' => esc_html__( 'Footer Menu', 'olsen-light' ),
) );

/*
 * Default hooks