Logging into Chrome is useful as it syncs bookmarks and other user data between devices.
This allows you to have the same Bookmarks on your Desktop/Laptop as on a Chromebook.

Click the 'Person' in the top right of Chrome, then, 'Turn on sync...'
Note: If you see your name, you are already logged in.

Simply enter in your email and password

If you want to keep your existing bookmarks and settings then select 'Link Data'. This will load your existing bookmarks into your Google Account. 

"Create a new profile" will start things from a blank slate.

Make sure to turn on Sync so all your settings and bookmarks and synced between different computers and Chromebooks. 

Now if you click the 'Person' in the top right of Chrome, you should see your email address displayed and the message that sync is on.