Hello,
Here is the code all together:
.sp-megamenu-parent>li>a, .sp-megamenu-parent>li>span, .sp-megamenu-parent .sp-dropdown li.sp-menu-item>a, .sp-megamenu-parent .sp-dropdown li.sp-menu-item span:not(.sp-menu-badge) {
font-family: 'Architects Daughter';
font-size: 19px;
}
Kindly, use this code in your custom CSS. You may adjust the font size value as per your need.
Note: Path towards custom CSS(Joomla 3): Extensions>Templates>Styles> Click on your current default template name then choose Template Options. Then find custom CSS within the custom code.
Best Regards