You need a published agent and its Embed code from Agent โ Deploy โ Website widget. Custom code on Webflow needs a paid site plan.
<script src="https://evasay.com/voice-widget.js" data-agent="AGENT_SLUG" async></script>
To show the agent on one page only, paste the code into that page's settings, under Custom code โ Before </body> tag, instead.
Under Agent โ Deploy โ Allowed websites, add each address your site opens at, for example https://your-site.webflow.io and https://www.example.com. Then your page can pass values and functions to the agent.