Once there is a new version, you'll be prompted by the below window:

 

Click Update to update DVDFab.

 

Or, you can check for update in Settings on the top right corner of DVDFab main interface.

 

And if there is a new version, you'll be prompted with the first window as mentioned above.

 

You can always go to www.dvdfab.cn/download.htm to download the latest version.