To boot Ubuntu on your Lenovo IdeaPad 310-15ISK, follow these steps: 1) Download the Ubuntu ISO file and create a bootable USB drive using software like Rufus or Etcher. 2) Access BIOS/UEFI settings by pressing the appropriate keys during startup. 3) Change the boot order by setting the USB drive as the first boot option or using the boot menu. 4) Save changes and exit the settings. 5) Boot from USB and select "Install Ubuntu" to begin the installation process. 6) Choose language, timezone, keyboard layout, disk partitioning options, and create a user account. 7) Restart your laptop and boot into Ubuntu.