Follow the steps below to check for/apply updates to your Chromebook.
1. At the bottom right, select the time.
2. Select Settings 
3.Select Menu 
About Chrome OS.
4. Select About Chrome OS
5. Click on Check for Updates
7. If there is an update available for your Chromebook the update will begin to download.
8. After the update has downloaded click on Restart to apply the update
Your Chromebook is now up to date!