I just want to try Bulma with Sage. Is that possible?
Bulma is already an option when installing Sage 9 with composer.
composer create-project roots/sage your-theme-name dev-master
I want it to be installed in Sage8! Is that possible?
You can install Bulma on Sage 8 using Bower via
bower install bulma. You can read more on theme development & building at the docs here.