To update Chrome:
Click on the 3 dots at the top right corner of Chrome (If Chrome is out of date, the icon may show as a green, yellow or red arrow instead of the 3 dots)
Click on Help
Choose About Google Chrome
Click the link to go to Chrome OS Settings
Click the button to Check for Updates
If Chrome is out of date, it will begin updating and when finished, it will have you reboot
If Chrome was way out of date, you may need to go through these steps again after it reboots because sometimes when Chrome is so far out of date, it needs to do this in two steps
How to know if Chrome is completely up to date:
Repeat steps 1-5 above
If Chrome is completely up to date, you will see Your Chromebook is up to date