First update the Neutrino composer package:
composer update newelement/neutrino
Next run the update command:
php artisan neutrino:update
The update command will migrate any database changes plus publish any assets and views.
If you attempt to update and run into an asset issue, try to run:
php artisan vendor:publish --provider="Newelement\Neutrino\NeutrinoServiceProvider" --tag=public --force