Dear Anne @annepohlmann
Yes you need to use CSS to tell the font to activate its alternative style set, for example here on a project i was doing recently:
._p-glyphs{ -moz-font-feature-settings: 'ss10'; -webkit-font-feature-settings: 'ss10'; font-feature-settings: 'ss10' on; }I used this CSS to turn on the use of Glyphs for the element called '._p-glyphs
You will need to use the developer tools to find out which element/text you wish to change and then in 'Lay Options - Custom CSS & HTML' target them and apply the font-feature-settings like your post above mentioned.
https://laytheme.com/documentation.html#custom-css-styling
For instance you will inspect an element it may be called - e.g site title text
.site-title-text{ font-feature-settings: ss0X; }Hope this helps! Good luck :)
Best
Richard