Add custom CSS class and ID names ?

Is there a way to add in my own class or ID name to the components so that I can use that unique name in the custom CSS area? I am trying to change the CSS Styles in the billing address area and make it look different than the order details area. All I can see to change in the HTML is that they are both inside <td> tags and the email address and the phone number are <a> tags. I cannot change one and not the other. I would be able to do that if there was a way to add in my own Class or ID identifiers in the editor tab. Here is a screen shot of what I am seeing and wanting to do: https://gyazo.com/3f04f4dec51ae0f79f495c355bf0a9df

I have tried to use this Custom CSS, but it is too broad in scope:
a { font-size: 26px; } a[href^="mailto:"], a[href^="tel:"] { font-size: 20px; } body, td, div { font-size: 16px; }