We asked them and they said to see their help section. It sounds like we would need to hire a coder if we want to use Charla on our site. Is this true? Here is what they said to us:

Thank you for contacting systeme.io.

You can try to add apps such as this via custom code: https://help.systeme.io/article/306-is-it-possible-to-insert-html-css-or-js-code

We are unable to make a recommendations as this lies beyond our expertise.

We are at your disposal for further assistance