Hide author and date on single post page

How do I hide the post author and date on the single post page in Issue?
I usually do this with CSS using display: none; Where does the CSS reside in Issue? If I change the CSS in the main Upfront theme will it be overwritten when Upfront is updated?

Better documentation on using Upfront Builder is needed.

Edited to add: I was able to suppress the display of the author and date by adding this code to the Issue child theme's style.css file.

.default .upfront-post-data-part .author, .default .upfront-post-data-part .author a {
    display: none;
}
.date-only .upfront-post-data-part .date_posted {
        display: none;
}