Listings are not responsive

Hello. I really enjoy your IMPress Listings plugin. The only problem is the listings do not display as responsive. My entire site/theme work as responsive. Only this plugin does not. I read your forum and found a similar problem and tried to add the snippet of code you suggested. I used the element inspector and it seems that the following bit of custom CSS will resolve the problem, but I don’t know where to put it. I have opened appearance>editor>child theme and placed it there, but there is not result. I also added it to a custom css plugin but that doesn’t work either. Can you point me to where I can edit the css file for the plugin? Also, is this the correct code?

NOTE: The site is password protected as it is still not finished. Password is “test”

.info-section-content {
    box-sizing: border-box;
    margin: 0px 0px 0.625em;
    padding: 0px 0.9375em;
    direction: ltr;
    position: relative;
    width: 100%;
    float: left;
    line-height: 1.4em;
    caret-color: #333333;
    font-family: 'Montserrat Light', 'Helvetica Neue', Helvetica, Helvetica, Arial, sans-serif;
    text-size-adjust: auto;
}

The page I need help with: [log in to see the link]