Press the Backlight key on the keyboard, usually Fn + Spacebar or Fn + Esc
Press the key with the keyboard light icon if your Lenovo model has one
Use Lenovo Vantage to enable keyboard backlight settings
Check the BIOS/UEFI settings for keyboard backlight options
Increase the backlight brightness by pressing the backlight key repeatedly
Make sure your Lenovo model supports a backlit keyboard