Lenovo 21DC - dual-boot installation?

[kalpana]

Can anyone point me to a guide to creating a dual-boot installation with existing Windows 11.

I have shrunk the initial windows partition, to create a new one to install Ubuntu. I get to the point of booting ubuntu from a USB stick but eventually end up with a console message:

(initramfs) Unable to find a medium containing a live file system

Where do I go from there?