You can customise the Conversagent launch icon directly within the Shopify Theme Editor.
To customise the knowledge that Conversagent has, or the way it talks to customers, go to Apps > Conversagent in the admin dashboard (outside of the theme editor) and adjust accordingly. Feel free to reach out to support@clevertar.com if you would like help with this.
If an embedded version of Conversagent fits your brand's guidelines, you can add an embedded Conversagent to your Shopify store too.