You saw a yellow banner in Dean Tools saying a new version is ready. Here's how to get it.
Go to the releases page. Click the .zip file under the newest version to download it.
Ignore the files labelled "Source code" — you want the .zip above them.
Find the Dean Tools folder on your Desktop (where you put it when you first installed). Delete it — drag it to the trash.
Then double-click the zip you just downloaded. Drag the new Dean Tools folder to your Desktop — same name, same place.
Go to chrome://extensions in your browser. Find UEU Dean Tools and click the reload button — the circular arrow.
That's it. You're on the new version.
Every version stays on the releases page. Download the one you want and follow these same steps.