You can find URLs of individual visualizations you've created at https://your-qliksense-address/single/. I think you should be able to embed them to an iframe in your website. Though note, that your users will still need to login in with their Qlik Sense credentials.
Do you mean there is nothing in the https://your-qliksense-address/single/ URL? What you should see is a list of your Qlik Sense apps. Do you in fact see any apps in the Hub for the user you are logging in with?