Append to container using class name instead of ID

Hi,

My company website is built using ReactJS, and does not contain any IDs throughout the markup.

I would like to insert custom HTML into a part of this site. However, the docs say that I must latch on to an ID specifically (https://www.qualtrics.com/support/website-app-feedback/creatives-tab/creative-types/custom-html-creative/). When I use an ID it works, but if I use a class or any other selector it does not work.

How can I work around this without making any changes to the website itself?

I just want to be able to select by .classname instead of #idname

Thanks,
Joe