how to add submenu in target theme

sorry, my site is : https://asianbudgettravel.com

What change did you make in .css file?

the changes i made before are regarding the font size on the menu. but since nothing changed, so i deleted the changes in the .css file

Can you re-attempt the change and post it here?
Are you using a Child Theme?

var {
font-size: 15px;
line-height: 21px;
}

yes I am using Child Theme

Try using

ul.dropdown a:link,
ul.dropdown a:visited {
 font-size: 15px;
 line-height: 21px;
}

I found this using Google Chrome’s Inspect Element tool, by simply right clicking on the menu link and selecting ‘Inspect element’.

Thank you. The font is bigger now, but the page Hong Kong is still in line with the Destination page. I am trying to place Hong Kong as a submenu for Destination page.

Here’s a tutorial for drop down menus.
https://ago.tanfa.co.uk/css/examples/menu/tutorial-h.html

thank you for your help. i haven’t chosen a parent page in the quick edit options.