Go to Google Fonts and select a font that you like.
Select the font weights by clicking the + button on the right. A sidebar will open that gives you two text snippets. Switch to the ‘@import’ option, then paste the snippet into your UI section or game description.
With this you should have successfully imported the font, so you should be able to style any parts of your UI like this:
body {
font-family: 'Kdam Thmor Pro', sans-serif;
}