Learn how to embed 3rd party apps into your project.
How to embed a 3rd party website
Embeds will show up for you and your client as a new tab. You can add a URL or an iframe embed that's provided to you by the 3rd party website. Not all websites has or allows embedding, so you should check the preview before expecing it to work.
If you want to embed Notion, you will need to use a 3rd party application such as https://embednotion.com/. Once you add your page to that website, they will provide an emebed code which you can paste on Queue.