You can install browser extensions like Cirrus Insight by setting a Group Policy for Google Chrome.
Take a look at these instructions and templates provided by Google.
Here is the extension information you'll need for setting a policy to install Cirrus Insight:
Extension ID: fmdomiplhgolgpibfdjjhgbcbkdcfkmk
Update URL: https://clients2.google.com/service/update2/crx
Simply restart the browser for the policy to take effect.
(Alternatively, you can set a policy in the Google Apps admin panel to install Chrome extensions like Cirrus Insight. Policies are enforced when users sign in to Chrome. For more information, check out the Simple Admin Guide to Installing Cirrus Insight.)