Adding Background Color to Text

Site URL: https://mylifetransforms.com

The web designer had made the first line in the Home Page have a black background. I changed the verbiage and want also to have a black background to the 2nd line.

The custom code she used is in the link. How do I do it myself? Thank you!

https://share.squarespace.com/04uY8vbj

Add to Home > design > Custom CSS

.homepage .desc-wrapper>p:nth-child(2) {
    background: black;
    display: inline-block;
    margin-bottom: 0;
}