Change font size of all elements

Add this code to the Custom CSS field on the Appearance tab of your widget’s settings:

/* FAQ title font and size */ 
.eui-widget-title{
  font-size: 24px !important;
}

/* FAQ category title font and size */ 
.eapps-faq-content-category-title-text{
		font-size: 22px !important;
}

/* FAQ question font and size */ 
.eapps-faq-content-category-item-question{
  font-size: 18px !important;
}

/* FAQ answer font and size */ 
.eapps-faq-content-category-item-answer-text{
  font-size: 18px !important;
}