Bind xbacklight-increase and xbacklight-decrease to some
keys and adjust xbacklight-step if you want the brightness to
increase/decrease in different steps then 10%.
You can also specify the steps amount with a prefix argument. E.g. C-50 <XF86MonBrightnessUp> would increase the brightness by 50.
With use-package the config could look like:
(use-package xbacklight
:bind (("<XF86MonBrightnessUp>" . xbacklight-increase)
("<XF86MonBrightnessDown>" . xbacklight-decrease)))