Keep in mind, that Steam on ChromeOS is best suited for higher-end hardware, like the Acer Chromebook 516 GE that we reviewed. The feature is live in the ChromeOS Beta Channel, which means you'll have to switch your device over to a somewhat unstable version of the operating system.
This is the best possible way to run Steam on ChromeOS. Google and Steam recently partnered to make it officially possible to run Steam on ChromeOS in beta.