Chromebooks do not have a Caps Lock key. Instead there is a search button, which in my opinion is completely useless when the address bar is a search. Use Control-L to highlight the address bar and type your search. You can switch your search button into a Caps Lock button.
Click on the bottom right hand corner of the Chromebook screen where the wifi signal is and choose settings.
In the settings, scroll down to "Keyboard settings" underneath the "Device" heading.
You can change the Search button from "Search" to "Caps Lock" from the drop down menu.